rails_ops

This Gem introduces an additional service layer for Rails: Operations. An operation is in most cases a business action or use case and may or may not involve one or multiple models. Rails Ops allows creating more modular applications by splitting them up into their different operations. Each operation is specified in a single, testable class.

To achieve this goal, this Gem provides the following building blocks:

• Various operation base classes for creating operations with a consistent interface and no boilerplate code.

• A way of abstracting model classes for a specific business action.

Requirements & Installation

Requirements

• RailsOps only works with Rails applications, with the following Rails versions being tested in the CI:
  • Rails 6.0.x
  • Rails 6.1.x
  • Rails 7.0.x
  • Rails 7.1.x
• Additionally, the following Ruby versions are covered by our unit tests:
  • 2.7.1
  • 3.0.1
  • 3.1.0
  • 3.2.0
  • 3.3.0
• Please see the unit test workflow for the combinations of the Rails & Ruby versions, as only compatible versions are tested with each other.
• Prior Rails and Ruby versions may be supported but they are not tested in the CI.
• Rails Ops' model operations require ActiveRecord but are database / adapter agnostic

Installation

1. Add the following to your Rails application's Gemfile:

   gem 'rails_ops'

2. Create an initializer file config/initializers/rails_ops.rb with the following contents:

   # Replace this with your authorization backend.
   require 'rails_ops/authorization_backend/can_can_can.rb'
   
   RailsOps.configure do |config|
     # Replace this with your authorization backend.
     config.authorization_backend = 'RailsOps::AuthorizationBackend::CanCanCan'
   end

3. Optional: If you want your operations to reside inside of app/operations and be scoped in the Operations namespace, create the directory app/operations and add the following code inside of the previously created initializer (after the RailsOps.configure block):

   # Remove the folder from the autoload paths
   app_operations = "#{Rails.root}/app/operations"
   ActiveSupport::Dependencies.autoload_paths.delete(app_operations)
   
   # Define the Operations module
   module Operations; end
   
   # Add the folder to the autoloader, but namespaced
   loader = Rails.autoloaders.main
   loader.push_dir(app_operations, namespace: Operations)
   
   # Add the folder to the watched directories (for re-loading in development)
   Rails.application.config.watchable_dirs.merge!({
     app_operations => [:rb]
   })

   Taken from this github issues comment.

Operation Basics

Placing and naming operations

• Operations generally reside in app/operations and can be nested using various subdirectories. They're all inside of the Operations namespace.

• Operations operating on a specific model should generally be namespaced with the model's class name. So for instance, the operation Create for the User model should generally live under app/operations/user/create.rb and therefore should be called Operations::User::Create.

• Operations inheriting from other operations should generally be nested within their parent operation. See the next section for more details.

• Operation classes should always be named after an action, such as Create, MoveToPosition and so on. Do not name an operation something like UserCreator or CreateUserOperation.

Heads-up: Correct namespacing

As explained in the previous section, operations should be namespaced properly. Operations can either live within a module or within a class. In most cases, operations are placed in the Operation module or rather one of its sub-modules. If, in some special case, operations are nested, they can reside inside of another operation class (but not inside of its file) as well.

When declaring an operation within a namespace,

• Determine whether the namespace you're using is a module or a class. Make sure you don't accidentally redefine a module as a class or vice-versa.

• If the operation resides within a module, make a module definition on the first line and the operation class on the second. Example:

  module Operations::Frontend::Navigation
    class DetermineActionsForStructureElement < RailsOps::Operation
      ...
    end
  end

• If the operation resides within a class, use a single-line definition:

  class Operations::User::Create::FromApi < Operations::User::Create
    ...
  end

Note that, when defining a namespace of which a segment is already known as a (model) class, you cannot just use the model classes name to refer to it:

module Operations::User
  class Create < RailsOps::Operation
    def perform
      # This DOES NOT work as `User` in this case refers to the module of
      # the same name defined on the first line of code.
      User.create(params)

      # This works as it takes an absolute namespace:
      ::User.create(params)
    end
  end
end

Basic operations

Every single operation follows a few basic principles:

• They inherit from {RailsOps::Operation}.

• They are called using the run or run! methods.

• They are parameterized using a params hash (and nothing else).

• They define a protected perform method which actually executes the operation. This is usually overridden in each operation and called exclusively by run or run!.

• They have a Context. See the respective chapter for more information.

So, an example of a very simple operation would be:

class Operations::PrintHelloWorld < RailsOps::Operation
  def perform
    puts "Hello #{params[:name]}"
  end
end

Running operations manually

There are various ways of instantiating and running an operation. The most basic way is the following:

op = Operations::PrintHelloWorld.new(name: 'John Doe')
op.run

There is even a shortcut for this:

Operations::PrintHelloWorld.run(name: 'John Doe')

Validations, run and run!

As you have noticed, there are two methods for running operations: run and run!. They behave exactly like save and save! of ActiveRecord: While the run! method raises an exception if there is a validation error, run would just return false (or true on success). As not every operation deals with models or ActiveRecord models, run does not only catch the ActiveRecord::RecordInvalid exception but also every exception that derives from {RailsOps::Exceptions::ValidationFailed}.

Catching custom exceptions in run

If you'd like to catch a custom exception if the operation is called using run, you can either derive this exception from {RailsOps::Exceptions::ValidationFailed} or else override the validation_errors method:

class Operations::PrintHelloWorld < RailsOps::Operation
  # Returns an array of exception classes that are considered as validation
  # errors.
  def validation_errors
    super + [SomeCustomException]
  end
end

Returning data from operations

All operations have the same call signatures: run always returns true or false while run! always returns the operation instance (which allows easy chaining). If you need to access data that has been generated / processed / fetched in the operation, create custom accessor methods:

class Operations::GenerateHelloWorld < RailsOps::Operation
  attr_reader :result

  def perform
    @result = "Hello #{params[:name]}"
  end
end

puts Operations::GenerateHelloWorld.run!(name: 'John Doe').result

Params Handling

Passing params to operations

Each single operation can take a params hash. Note that it does not have to be in any relation with ActionController's params - it's just a plain ruby hash called params (in fact, it is a Object::HashWithIndifferentAcces, more on that later).

Params are assigned to the operation via their constructor:

Operations::GenerateHelloWorld.new(foo: :bar)

If no params are given, an empty params hash will be used. If a ActionController::Parameters object is passed, it will be permitted using permit! and converted into a regular hash.

Accessing params

For accessing params within an operation, you can use params or osparams. While params directly returns the params hash, osparams converts them into an OpenStruct first. This allows easy access using the 'dotted notation':

def perform
  # Access a param using the `params` method
  params[:foo]

  # Access a param using the `osparams` method
  osparams.foo
end

Note that both params and osparams return independent, deep duplicates of the original params hash to the operation, so the hashes do not correspond.

The hash accessed via params is a always Object::HashWithIndifferentAccess.

Validating params

You're strongly encouraged to perform a validation of the parameters passed to an operation, as unvalidated params pose a security threat. This can be done in several ways:

• Using a schemacop schema:

  class Operations::PrintHelloWorld < RailsOps::Operation
    schema3 do
      str! :name
    end
  
    def perform
      puts "Hello #{params[:name]}"
    end
  end

  This is the recommended way of performing basic params validation. Please see the next section Schema best practices for more information.

  See documentation of the Gem schemacop for more information on how to specify schemata.

• Manually using a policy (see chapter Policies):

  class Operations::PrintHelloWorld < RailsOps::Operation
    policy do
      unless osparams.name && osparams.name.is_a?(String)
        fail 'You must supply the "name" argument.'
      end
    end
  
    def perform
      puts "Hello #{params[:name]}"
    end
  end

• Using a business model (see chapter Model Operations).

Schema best practices

As previously mentioned, using schema from the schemacop gem is the recommended way to validate params passed in to an operation. In general, it's recommended to use version 3 of schemacop, i.e. either use schema3 to specify the schema, or set the default schema version to 3:

# config/initializers/rails_ops.rb
RailsOps.configure do |config|
  config.default_schemacop_version = 3
end

Internal code

When writing a schema for an operation which is only used internally (e.g. called from another operation, or called from a part of the code where you control the params, e.g. a rake task), it's recommended to specify the types of all items, as this will catch any mismatched data. For example:

class Operations::PrintHelloWorldWithId < RailsOps::Operation
    schema3 do
      int! :id
      str! :name
    end

    def perform
      puts "Hello #{params[:name]}, your ID is: #{params[:id]}"
    end
  end

Called within controllers

On the other hand, operations which are called within controllers (e.g. to encapsulate an update operation of a model) should not assume any types, and instead use model validations (if applicable) to validate the correctness of the data. In this case, the schema should only be used to filter the params. As such, it's recommended to use obj to specify params which are not strings, as this will allow anything (but only the specified values). An example would be:

module Operations::User
  class Update < RailsOps::Operation::Model::Update
    schema3 do
      int! :id
      hsh? :user do
        obj! :age
        str! :first_name
        obj! :is_active
      end
    end
  end
end

Validating that age is an integer and is_active then should be done with a validation in the User model, as this will also populate the model errors, which in turn will display the error in the form. If you were to validate the type of the data here, it would raise a Schemacop::Exceptions::ValidationError exception, which you would need to handle seperately.

Finally, when additional, obsolete params are supplied, the schema validation would also fail. To have a similar behavious to the strong params from Rails, which drop non-whitelisted params without raising an exception, you can use the ignore_obsolete_properties option. This will simply ignore and drop any params which are not explicitly whitelisted:

module Operations::User
  class Update < RailsOps::Operation::Model::Update
    schema3 ignore_obsolete_properties: true do
      int! :id
      hsh? :user do
        obj! :age
        str! :first_name
        obj! :is_active
      end
    end
  end
end

Catching schema validation errors

When an operation is called from a controller (via the run or run! method) and a schema validation excaption occurs, the controller will respond with an empty body and a status code 400 (bad request). This behaviour is enabled by default, but can be disabled with the rescue_validation_error_in_controller config option:

# config/initializers/rails_ops.rb
RailsOps.configure do |config|
  config.rescue_validation_error_in_controller = false
end

Generally, this should be left enabled, as sending invalid data to the controller should not result in an internal server error, but rather in a "client error".

Please note that this behaviour is disabled in development mode, as the full exception messages are useful for debugging purposes.

Policies

Policies are nothing more than blocks of code that run either at operation instantiation or before / after execution of the perform method and can be used to check conditions such as params or permissions.

Policies are specified using the static method policy, inherited to any sub-classes and executed in the order they were defined.

class Operations::PrintHelloWorld < RailsOps::Operation
  policy do
    puts 'This runs first'
  end

  policy do
    puts 'This runs second'
  end

  def perform
    puts 'This runs third'
    puts 'Oh, and hello world'
  end
end

The basic idea of policies is to validate input data (the params hash) or other conditions such as authorizations or locks.

Some checks might still need to be performed directly within the perform method. Use policies as much as possible though to keep things separated.

The return value of the policies is discarded. If a policy needs to fail, raise an appropriate exception.

Policy chains

As mentioned above, policies can be executed at various points in your operation's lifecycle. This is possible using policy chains:

• :on_init

  Policies in this chain run after the operation class is instantiated.

• :before_perform

  Policies in this chain run immediately before the perform method is called. Obviously this is never called if the operation is just instantiated and never run. This is the default chain.

• :before_model_save

  This only applies to operations deriving from RailsOps::Operation::Model and its descendants. Policies in this chain run after nested model operations are performed immediately before the "main" model is saved.

• :before_nested_model_ops

  This only applies to operations deriving from RailsOps::Operation::Model and its descendants. Policies in this chain run after nested model operations are performed before performing any nested model operations.

• :after_perform

  Policies in this chain run immediately after the perform method is called. Obviously this is never called if the operation is just instantiated and never run. Also, this does not run if an exception occurs while performing the operation.

The policy chain (default is :before_perform) can be specified as the first argument of the policy class method:

class MyOp < RailsOps::Operation
  policy :on_init do
    puts 'This is run once the operation has been instantiated.'
  end

  policy do
    puts 'This is run before the operation is performed.'
  end
end

The order inside the same policy chain depends on the time when a block was added. You can prepend an action to a policy chain by setting :prepend_action to true:

class MyOp
  policy :on_init, prepend_action: true do
    puts 'This is run first the operation has been instantiated.'
  end

In this case the model is not yet set. That will happen later in the :on_init chain. It is also important to note, that this block is not guaranteed to be run first in the chain, if multiple blocks have set :prepend_action to true.

Calling sub-operations

It is possible and encouraged to call operations within operations if necessary. As the basic principle is to create one operation per business action, there are cases where nesting operations can be very beneficial.

Let's say we have an operation User::Create that creates a new user. The operation should also assign the newly created user to a default Group after creation. In this case, we basically have two separate operations that should not be combined in one. For this case, use sub-operations:

class Operations::User::Create < RailsOps::Operation
  def perform
    user = User.create(params)
    run_sub! AssignToGroup, user: user, group: Group.default
  end
end

Every operation offers the methods {RailsOps::Mixins::SubOps.run_sub}, {RailsOps::Mixins::SubOps.run_sub!} and {RailsOps::Mixins::SubOps.sub_op}. The latter one just instantiates and returns a sub operation.

So why don't we just create and call the sub-operation directly? The reason lies within the context that is automatically adapted and passed to the sub-operation and enables to maintain the complete call stack and allows to pass on context information such as the current user.

A note on validations

As always when calling operations, you can decide whether an execution should raise an exception on validation errors or else just return false by using the bang or non-bang methods.

For nested operations, we must give this fact a little more thought. Consider the following case:

• Operation A is called using run.
• Operation A calls operation B using run_sub!.
• Operation B throws a validation exception.

In this case, it is now expected that A returns non-gracefully, even though it's called using the non-bang method. The reason is that A explicitly used the bang-method for calling the sub-op.

However, as calling A catches any validation errors, it will also catch the validation errors raised by a sub-operation. For this case, calling run_sub! catches any validation errors and re-throws them as {RailsOps::Exceptions::SubOpValidationFailed} which is not caught by the surrounding op.

Contexts

Most operations make use of generic parameters like the current user or an authorization ability. Sure this could all be passed using the params hash, but as this would have to be done for every single operation call, it would be quite cumbersome.

For this reason Rails Ops provides a feature called Contexts. Contexts are simple instances of {RailsOps::Context} that may or may not be passed to operations. Contexts can include the following data:

• A user object

  This is meant to be the user performing the operation. In a controller context, this usually referred to as current_user.

• The session object

  This is the rails session object (can be nil).

• An ability object

  This is an ability object (i.e. cancan(can)) which holds the permissions currently available. This is used for authorization within an operation.

• The operations chain

  The operations chain contains the call stack of operations. This is automatically generated when calling a sub-op or triggering an op using an event (see chapter Events for more information on that).

• URL options

  Rails uses a hash named url_options for generating URLs with correct prefix. This information usually comes from a request and is automatically passed to the operation context when calling an operation from a controller. This hash is used by {RailsOps::Mixins::Routes}.

• View context

  If the operation has been created from within a controller, the property view includes the current view context. Only use this for frontend operations that will always be called from a controller.

• Called via hook

  called_via_hook is a boolean indicating whether or not this operation was called by a hook (true) or by a regular method call (false). We will introduce hooks below.

Instantiating contexts

Contexts behave like a traditional model object and can be instantiated in multiple ways:

context = Context.new(user: current_user, params: { foo: bar })

# Another way
context = Context.new
context.user = current_user

Feeding contexts to operations

Contexts are assigned to operations via the operation's constructor:

my_context = RailsOps::Context.new
op = Operations::PrintHelloWorld.new(my_context, foo: :bar)

For your convenience, contexts also provide run and run! methods:

my_context.run Operations::PrintHelloWorld, foo: :bar

Sub-operations

When calling a sub-operation either using the corresponding sub-operation methods or else using events, a new context is automatically created and assigned to the sub-operation. This context includes all the data from the original context. Also, the operations chain is automatically complemented with the parent operation.

This is called context spawning and is performed using the {RailsOps::Context.spawn} method.

Hooks

In some cases, certain actions must be hooked in after execution of an operation. While this can certainly be done with sub-operations, it is not always desirable as the triggering operation should not always know of the additional ones it's triggering:

• Operations::User::Create creates a user, but also creates a group object using Operations::Group::Create. This is an example for sub-ops.

• Operations::User::Create creates a user. Whenever a user is created, another part of the application needs to generate a todo for the admin to approve this user. This would be an example for hooks.

Hooks are pretty simple: Using the file config/hookup.rb, you can specify which operations should be triggered after which operations. These operations are then automatically triggered after the original operation's perform (in the run method).

Defining hooks

Hooks are defined in a file named config/hookup.rb in your local application. In development mode, this file is automatically reloaded on each request so there is no need to restart the application server for this while developing.

Defining hooks is as simple as defining a target operation and one or more source operations.

RailsOps.hookup.draw do
  run 'Operations::Notifications::User::SendWelcomeEmail' do
    on 'Operations::User::Create'
  end

  run 'Operations::Todos::GenerateUserApprovalTodo' do
    on 'Operations::User::Create'
  end

  run 'Operations::Notification::SendTodoNotification' do
    on 'Operations::Todos::GenerateUserApprovalTodo'
  end
end

Operations hooks are always performed in the order they are defined.

Events

Each operation can throw different events. The event :after_run is automatically triggered after each operation's execution and should be sufficient for most cases. However, it is also possible to trigger custom events in the perform method:

def perform
  trigger :custom_event_name, { some: :params }
end

This can be hooked by specifying the custom event name in your hookup configuration:

on Operations::User::Create, :custom_event_name do
  perform Operations::Notifications::User::SendWelcomeEmail
end

In most cases though, situations like these should rather be handled by explicitly calling a sub-operation.

Hook parameters

For each hook that is called, at set of parameters is passed to the respective operations. When calling events manually (see section Events), you can manually specify the parameters. For the default event :after_run, the set of parameters is defined by the operation method after_run_trigger_params. In the default case, this returns an empty array. Some operation base classes, like for instance RailsOps::Operation::Model, override this method to supply a custom set of parameters. See your respective base class for more information.

Be advised: It is not usually desirable to provide a very custom param set that is tailored to one particular target operation. Trigger parameters should be as generic as possible as specific cases should rather be handled using sub-ops.

Operations can be used to write adapters (glue operations) in order to hook into an operation with incompatible parameters. Create a glue operation that hooks into the source operation and prepares the params specifically for the target operation, which is then called using a sub-operation or the hooking system.

Check if called via hook

You can determine whether your operation has been (directly) called via a hook using the called_via_hook context method:

def perform
  puts 'Called via hook' if context.called_via_hook
end

Note that this property never propagates, so when calling a sub-operation from an operation that has been called using a hook, called_via_hook of the sub-operation is set to false again.

Authorization

Operations called via hooks perform normal authorization per default. You can turn this off by switching off the gobal option config.trigger_hookups_without_authorization.

Authorization

Rails Ops offers backend-agnostic authorization using so-called authorization backends.

Authorization basically happens by calling the method authorize! (or authorize_only!, more on that later) within an operation. What exactly this method does depends on the authorization backend specified.

Authorization backends

Authorization backends are simple classes that supply the method authorize!. This method, besides the operation instance, can take any number of arguments and is supposed to perform authorization and raise if the authorization failed.

The authorization backend can be configured globally using the authorization_backend configuration setting, which can be set to the name of your backend class.

Example initializer:

RailsOps.configure do |config|
  config.authorization_backend = 'RailsOps::AuthorizationBackends::CanCanCan'
end

RailsOps ships with the following backend:

• RailsOps::AutorizationBackend::Cancancan

  Offers integration of the cancancan Gem (which is a fork of the cancan Gem).

Performing authorization

Authorization is generally performed by calling authorize! in an operation. The arguments, along with the operation instance, are passed on to the authorize! method of your authorization backend. Basically, you can call authorize! anywhere in your operation, but bear in mind that if your authorization requires certain data (i.e. the params hash), your authorization calls should occur after that certain data is available.

class MyOp < RailsOps::Operation
  def perform
    authorize! :read, :some_area
  end
end

Usually though, authorization, as other pre-conditions, are called within policies:

class MyOp < RailsOps::Operation
  policy do
    authorize! :read, :some_area
  end
end

In many cases, you'd like the authorization to run no matter if the operation ever runs. For this case, use the :on_init policy chain:

class MyOp < RailsOps::Operation
  policy :on_init do
    authorize! :read, osparams.some_record
  end
end

See section Policy chains for more information.

Ensure that authorization has been performed

As it is a very common programming mistake to mistakenly omit calling authorization, Rails Ops offers a solution for making sure that authorization has been called in every operation.

This is done by calling ensure_authorize_called! on your operation. This will raise an exception if no authorization has been performed. This method is automatically called in run or run! after the execution of the perform method.

This method only applies if authorization is currently enabled (see next section), otherwise it does nothing.

It is implemented so that every call to authorize! sets an instance variable of the respective operation to true, and ensure_authorize_called! checks this instance variable on calling.

Sometimes you might want to call authorization that should not count for this check, i.e. some base authorization that needs to be complemented with some specific authorization code. In these cases, use authorize_only!:

def perform
  authorize_only! :foo, :bar

  # The following will fail as authorize_only! calls do not count as authorized.
  ensure_authorize_called!
end

This method otherwise does exactly the same as authorize! (in fact, it's the underlying method used by it).

Param authorization

Using the static operation method authorize_param, you can perform additional authorization checks when specific params are passed to the operation. This allows you to disallow certain params, i.e. when updating a model and wanting to restrict the user to certain fields.

When using non-model operations (operations not inheriting from RailsOps::Operation::Model or one of its subclasses), authorize_param requires you to specify an action and optional, additional args or a block that performs custom authorization:

class Operations::User::DoSomething < RailsOps::Operation
  schema do
    opt :user do
      opt :name
      opt :group_id
    end
  end

  # Example with passing an action and additional args
  authorize_param %i(user group_id), :update_group_id, :some_subject

  # Example with passing a block
  authorize_param %i(user group_id) do
    # This is executed in the context of the op instance
    fail 'Some message' unless user_has_permission?
  end

The first param always provides the path to the param to be checked for existence. Note that this only works with nested hash structures, but not with arrays and other objects. The first level of the params hash is always using indifferent access, so it does not matter whether you pass a symbol or a string as the first path segment. For additional path segments, it needs to match the actual type that is used as hash key. For example: [:user, 'group_id'].

For model operations, you only need to pass a path and an action if you want to perform authorization on your model:

class Operations::User::Create < RailsOps::Operation::Model::Create
  schema do
    opt :user do
      opt :name
      opt :group_id
    end
  end

  authorize_param %i(user group_id), :assign_group_id

Disabling authorization

Sometimes you don't want a specific operation to perform authorization, or you don't want to perform any authorization at all.

For this reason, Rails Ops allows you to disable authorization globally, per operation or per operation call (i.e. an operation should generally perform authorization, but not in a specific case). If authorization is disabled, all calls to authorize! won't have any effect and will never fail. Also, it is not ensured that authorization has been performed as it would always fail (see previous section).

Rails Ops offers multiple ways of disabling authorization:

• By not configuring any authorization backend.

• By calling the class method without_authorization:

  class MyOp < RailsOps::Operation
    without_authorization
  end

  If the operation is invoked using controller integration, this also disables the controller-side check that makes sure an authorization method is called.

  This does not disable authorization for any sub operations. See the next section for information on how to disable sub operation authorization.

• By invoking one or more operations in a RailsOps.without_authorization block:

  RailsOps.without_authorization do
    # Authorization will be disabled even if `SomeOperation` itself would
    # otherwise perform authorization.
    SomeOperation.run
  end

  Within operations, you can also use the instance method without_authorization which does the same thing as the global one (it is just a shortcut and can therefore be used interchangeably):

  class MyOp < RailsOps::Operation
    def perform
      without_authorization do
        run_sub! SomeOtherOperation
      end
    end
  end

  Note that when calling without_authorization this does not only apply to other operations called, but also to the operation you're currently in:

  class MyOp < RailsOps::Operation
    def perform
      without_authorization do
        # The following line does nothing, as authorization is currently
        # disabled.
        authorize! :read, :some_area
      end
    end
  end

  However, please note that the block form of authorize_param is still executed, as there might be code in the block that does not rely on the authorization backend:

  class MyOp < RailsOps::Operation
    def perform
      without_authorization
  
      authorize_param %i[user group_id] do
        # This block will be called
        fail if ENV['GROUP_ID'].blank?
      end
    end
  end

  If you want to skip the block, use authorization_enabled? to check whether the authorization is enabled:

  class MyOp < RailsOps::Operation
    def perform
      without_authorization
  
      authorize_param %i[user group_id] do
        next unless authorization_enabled?
  
        # Do authorization calls
      end
    end
  end

Model Operations

One of the key features of RailsOps is model operations. RailsOps provides multiple operation base classes which allow convenient manipulation of active record models.

All of the model operation classes, including more specialized base classes, inherit from {RailsOps::Operation::Model} (which in turn inherits from {RailsOps::Operation} as every operation base class).

The key principle behind these model classes is to associate one model class and one model instance with a particular operation.

Setting a model class

Using the static method model, you can assign a model class that is used in the scope of this operation.

class SomeOperation < RailsOps::Operation::Model
  model User
end

You can also directly extend this class by providing a block. If given, this will automatically create a new, anonymous class that inherits from the given base class and run the given block in the static context of this class:

class SomeOperation < RailsOps::Operation::Model
  model User do
    # This code only runs in a dynamically created subclass of `User` and does
    # not affect the original model class.
    validates :name, presence: true
  end
end

You do not even have to specify a base class. In this case, the class returned by the static method default_model_class (default: {ActiveType::Object}) will be used as base class:

class SomeOperation < RailsOps::Operation::Model
  model do
    # See ActiveType documentation for more information on virtual attributes.
    attribute :name
  end
end

Obtaining a model instance

Model instances can be obtained using the instance method model, which is not to be confused with the class method of the same name. Other than the class method, the instance method instantiates and returns a model object with the type / base class specified using the model class method:

class SomeOperation < RailsOps::Operation::Model
  model User

  def perform
    # This returns an instance of the 'User' class. To be precise: This example
    # does not work out-of-the-box as this base class is abstract and does not
    # implement the `build_model` method. But more on that later.
    model
  end
end

The instance method model only instantiates a model once and then caches it in the instance variable @model. Therefore, you can call model multiple times and always get back the same instance.

If no cached instance is found, one is built using the instance method build_model. Note that this method is not provided by the Model base class but only implemented in its subclasses. You can implement and override this method to your liking though.

Loading models

Using the base operation class {RailsOps::Operation::Model::Load}, a model can be loaded. This is done by implementing the build_model mentioned above. In this particular case, the find method of the statically assigned model class is used in conjunction with an ID extracted from the operation's params.

class Operations::User::Load < RailsOps::Operation::Model::Load
  model User
end

# The operation does not have to be performed to access the model instance.
op = Operations::User::Load.new(id: 5)
op.model.id # => 5

Note that this base class is a bit of a special case: It does not provide an implementation of the perform method and does not need to be run at all in order to load a model (in fact, it cannot be run unless you override the perform method). This is very useful when, for example, displaying a form based on a model instance without actually performing any particular action such as updating a model.

Specifying ID field

Per default, the model instance is looked up using the field id and the ID obtained from the method params using params[:id]. However, you can customize this field name by overriding the method model_id_field:

class Operations::User::Load < RailsOps::Operation::Model::Load
  model User

  def model_id_field
    :some_other_id_field
  end
end

Locking

In most cases when you load a model, you might want to lock the corresponding database record. RailsOps is configured to automatically perform this locking at time of loading. However, you can override the default behavior using the option {RailsOps.config.lock_models_at_build}.

This behavior can also be overwritten per operation using the lock_model_at_build class method:

class Operations::User::Update < RailsOps::Operation::Model::Update
  model ::User
  lock_model_at_build false # Takes `true` if no argument is passed
end

Please note that for performance reasons, the Load operation (and any operations inheriting from it) use a shared lock, i.e. it issues an LOCK IN SHARE MODE / FOR SHARE statement. The Update and Destroy operations (as well as operations inheriting from it) however use the default lock method of ActiveRecord, which will issue an exclusive lock.

If you want to change the mode, you can use the lock_mode DSL method, which has two possible modes:

• :shared for the shared lock mode
• :exclusive for the exclusive lock mode

For example, if you have an operation loading a record which you'd want to lock exclusively, you'd need to write the following:

class Operations::User::Update < RailsOps::Operation::Model::Load
  model ::User
  lock_mode :exclusive
end

One caveat is, that shared locking is only supported for MySQl (MariaDB), Postgresql and Oracle DB databases, any other database will always use an exlusive lock.

You can also dynamically enable or disable locking by creating an instance method lock_model_at_build?:

class Operations::User::Update < RailsOps::Operation::Model::Load
  model ::User

  protected

  def lock_model_at_build?
    # Example: Lock based on a parameter
    osparams.lock
  end
end

Creating models

For creating models, you can use the base class {RailsOps::Operation::Model::Create}.

This class mainly provides an implementation of the methods build_model and perform.

The build_model method builds a new record using the operation's parameters. See section Parameter extraction for create and update for more information on that.

The perform method saves the record using save!.

class Operations::User::Create < RailsOps::Operation::Model::Create
  schema do
    req :user do
      opt :first_name
      opt :last_name
    end
  end

  model ::User
end

As this base class is very minimalistic, it is recommended to fully read and comprehend its source code.

Overriding the perform method

While in many cases there is no need for overriding the perform method, this can be useful i.e. when assigning or altering properties manually:

def perform
  model.some_value = 42
  model.first_name.upcase!
  super # Saves the record
end

Updating models

For updating models, you can use the base class {RailsOps::Operation::Model::Update} which is an extension of the Load base class.

This class mainly provides an implementation of the methods build_model and perform.

The build_model method updates a record using the operation's parameters. See section Parameter extraction for create and update for more information on that.

The perform method saves the record using save!.

class Operations::User::Update < RailsOps::Operation::Model::Update
  schema do
    req :id
    req :user do
      opt :first_name
      opt :last_name
    end
  end

  model ::User
end

As this base class is very minimalistic, it is recommended to fully read and comprehend its source code.

As with Create operations, the perform method can be overwritten at your liking.

Destroying models

For destroying models, you can use the base class {RailsOps::Operation::Model::Destroy} which is an extension of the Load base class.

This class mainly provides an implementation of the method perform, which destroys the model using its destroy! method.

class Operations::User::Destroy < RailsOps::Operation::Model::Destroy
  schema do
    req :id
  end

  model ::User
end

As this base class is very minimalistic, it is recommended to fully read and comprehend its source code.

Parameter extraction for create and update

As mentioned before, the Create and Update base classes provide an implementation of build_model that assigns parameters to a model.

The attributes are determined by the operation instance method extract_attributes_from_params - the name being self-explaining. See its source code for implementation details.

Model authorization

While you can use the standard authorize! method (see chapter Authorization) for authorizing models, RailsOps provides a more convenient integration.

Basic authorization

Model authorization can be performed via the operation instance methods authorize_model! and authorize_model_with_authorize_only! (see chapter Authorization for more information on the difference between these two).

These two methods provide a simple wrapper around authorize! and authorize_only! that casts the given model class or instance to an active record object. This is necessary if the given model class or instance is a (possibly anonymous) extension of an active record class for certain authorization backends to work. Therefore, use the specific model authorization methods instead of the basic authorization methods for authorizing models.

If no model is given, the model authorization methods automatically obtain the model from the instance method model.

Automatic authorization

All model operation classes provide the operation instance method model_authorization which is automatically run at model instantiation (this is done using an :on_init policy). The purpose of this method is to perform an authorization check based on this model.

While you can override this method to perform custom authorization, RailsOps provides a base implementation. Using the class method model_authorization_action, you can specify an action verb that is used for authorizing your model.

class Operations::User::Load < RailsOps::Operation::Model::Load
  model User

  # This automatically calls `authorize_model! :read` after operation
  # instantiation.
  model_authorization_action :read
end

Note that using the different model base classes, this is already set to a sensible default. See the respective class' source code for details.

Lazy model update authorization

In case of operations inheriting from RailsOps::Operation::Model::Update, you can specify the model_authorization_action to be lazy, meaning that it will only be checked when performing the operation, but not on initialization. This can be useful for displaying readonly forms to users which have read-permissions only:

class Operations::User::Update < RailsOps::Operation::Model::Update
  model User

  # This automatically calls `authorize_model! :read`. Because it is set to be
  # `lazy`, the authorization will only run when the operation is actually
  # *performed*, and not already at instantiation.
  model_authorization_action :update, lazy: true
end

Model nesting

Using active record, multiple nested models can be saved at once by using accepts_nested_attributes_for. While this is generally supported by RailsOps, you may want to consider saving nested models using their own operation.

For this case, RailsOps' create and update model operations provide the method nest_model_op.

class Operations::User::Create < RailsOps::Operation::Model::Create
  schema do
    opt :user do
      opt :name
      opt :group_attributes
    end
  end

  model ::User
  nest_model_op :group, Operations::Group::Create
end

class Operations::Group::Create < RailsOps::Operation::Model::Create
  schema :group do
    opt :name
  end

  model ::Group
  nest_model_op :group, Operations::Group::Create
end

In this example, the parent operation Operations::User::Create automatically instantiates a Group::Create operation and passes all the parameters to it that the parent operation received under group_attributes. The group is saved first. If this is successful, the user is saved.

Note that this feature only works with belongs_to associations with autosave set to false and is not compatible with accepts_nested_attributes_for:

class User
  belongs_to :group, autosave: false
end

Param key

When nesting a model operation, the sub operation is called automatically by RailsOps. For this purpose, it needs to know which param_key to use for calling the sub operation, e.g. user: { name: 'Jane Doe' }. Normally, this is derived by calling <sub-op-model-class>.model_name.param_key. If your operation for some reason expects a different param key, you can specify it using the option param_key, e.g.:

# Operation Operations::Group::Create will receive the following params:
#   { my_custom_key: { ... } }
nest_model_op :group, Operations::Group::Create, param_key: :my_custom_key

Custom parameters

In the above examples, all group_attributes are automatically passed to the sub operation. To customize this further, provide a block to the nest_model_op method:

nest_model_op :group, Operations::Group::Create do |params|
  params.merge(custom_override: :some_value)
end

This block receives the params hash as it would be passed to the sub operation and allows to modify it. The block's return value is then passed to the sub-operation. Do not change the params inplace but instead return a new hash.

Single-table inheritance

Model operations also support STI models (Single Table Inheritance). However, there is the caviat that if you do extend your model in the operation (e.g. model Animal do { ... }), RailsOps automatically creates an anonymous subclass of the given class (e.g. Animal). Operations will always load / create models that are instances of this anonymous class.

Consider the following operation:

class Animal < ApplicationRecord; end
class Bird < Animal; end
class Mouse < Animal; end

class LoadAnimal < RailsOps::Operation::Model::Load
  model Animal do
    # Something
  end
end

bird = Bird.create
op_bird = LoadAnimal.new(id: bird.id)

bird.class    # => Class "Bird", extending "Animal"
op_bird.class # => Anonymous class, extending "Animal", not "Bird"

Record extension and virtual records

Transactions

Controller Integration

While RailsOps certainly does not have to be used from a controller, it provides a mixin which extends controller classes with functionality that lets you easily instantiate and run operations.

Installing

Controller integration is designed to be non-intrusive and therefore has to be installed manually. Add the following inclusion to the controllers in question (usually the ApplicationController base class):

class ApplicationController
  include RailsOps::ControllerMixin
end

Basic usage

The basic concept behind controller integration is to instantiate and potentially run a single operation per request. Most of this guide refers to this particular use case. See section Multiple operations per request for more advanced solutions.

The following example shows the simplest way of setting and running an operation:

class SomeController < ApplicationController
  def some_action
    run! Operations::SomeOperation
  end
end

Separating instantiation and execution

In the previous example, we instantiated and ran an operation in a single statement. While this might be feasible for some "fire-and-forget" controller actions, you might want to separate instantiation from actually running an operation.

For this reason, RailsOps' controller integration is designed to always use a two-step process: First the operation is instantiated and assigned to the controller instance variable @op, and then it's possibly executed.

In the following example, we do exactly the same thing as in the previous one, but with separate instantiation and execution:

class SomeController < ApplicationController
  def some_action
    # The following line instantiates the given operation and assigns the
    # instance to `@op`.
    op Operations::SomeOperation

    # The following line runs the operation previously set using `op` using
    # the operations `run!` method. Note that `run` is available as well.
    run!
  end
end

The methods run and run! always require you to previously instantiate an operation using the op method.

This can be particularly useful for "combined" controller methods that either display a form or submit, i.e. based on the HTTP method used.

def update_username
  # As above operation extends RailsOps::Model, we can already access op.model
  # (i.e. in a form) without ever running the operation. Therefore, we
  # instantiate the operation even if it is a GET request.
  op Operations::User::UpdateUsername

  # In this example, the operation is only run on POST requests.
  if request.post? && run
    redirect_to users_path
  end
end

Checking for operations

Using the method op?, you can check whether an operation has already been instantiated (using op).

Model shortcut

RailsOps conveniently provides you with a model instance method, which is a shortcut for op.model. This is particularly useful since this is available as a view helper method as well, see next section.

You can check whether a model is available by using the model? method, which is available in both controllers and views.

View helper methods

The following controller methods are automatically provided as helper methods which can be used in views:

• op
• model
• op?

It is very common to use model for your forms:

= form_for model do |f|
  - # Form code goes here

Parameters

As you've probably noticed in previous examples, we did not provide any parameters to the operation.

Per default, the params hash is automatically provided to the operation at instantiation. To be more precise: The params hash is filtered not to include certain fields (see {RailsOps::ControllerMixin::EXCEPT_PARAMS}) that are most commonly not used by operations (e.g. the authenticity_token).

This is achieved using the private op_params method. Overwrite it to your needs if you have to adapt it for the whole controller.

Alternatively, you can pass entirely custom params to an operation via the op method:

op SomeOperation, some_param: 'some_value'

You can also combine these two approaches:

# This example takes the pre-filtered op_params hash and applies another, custom
# filter before passing it to the operation.
op SomeOperation, some_param: op_params.slice(:some_param, :some_other_param)

Authorization ensuring

For security reasons, RailsOps automatically checks after each action whether authorization has been performed. This is to avoid serving an action's response without ever authorizing.

The check is run in the after_action named ensure_operation_authorize_called! and only applies if an operation class has been set.

Note that this check also doesn't apply if the corresponding operation uses without_authorization (see section Disabling authorization for more information on this).

You can disable authorization ensuring by setting the global config option config.ensure_authorize_called = false.

Context

When using the op method to instantiate an operation, a context is automatically created. The following fields are set automatically:

• params (as described in subsection Parameters)
• user (uses current_user controller method if available, otherwise nil)
• ability (uses current_ability controller method if available, otherwise nil)
• session (uses the session controller method)
• url_options (uses the url_options controller method)

Multiple operations per request

RailsOps does not currently support calling multiple operations in a single controller action out-of-the-box. You need to instantiate and run it manually.

Another approach is to create a parent operation which calls multiple sub-operations, see section Calling sub-operations for more information.

Operation Inheritance

Generators

RailsOps features a generator to easily create a structure for common CRUD-style constructs. The generator creates the CRUD operations, some empty view files, a controller and adds an entry in the routing file.

This is e.g. useful when adding a new model to an application, as the basic structure is usually rather similar.

Usage

Run the generator using the operation generator, specifying the name of the operation class:

rails g operation User

This will generate the following operations:

• app/operations/user/load.rb
• app/operations/user/create.rb
• app/operations/user/update.rb
• app/operations/user/destroy.rb

as well as the controller app/controllers/users_controller.rb and the following empty view files:

• app/views/users/index.html.haml
• app/views/users/show.html.haml
• app/views/users/new.html.haml
• app/views/users/edit.html.haml

It will also add the entry resources :users to the config/routes.rb file.

If you want to skip the controller, the views or the routes, you can do so using the flags:

• --skip-controller
• --skip-routes
• --skip-views

Or if you want to skip them all: --only-operations.

If you want to skip a certain action, you can do so using the flags:

• --skip-index
• --skip-show
• --skip-create
• --skip-update
• --skip-destroy

This will skip the creation of the respective route, controller action, view file and the operation itself. For --skip-create, the new action will also be skipped and for --skip-update, the edit action will be skipped respectively.

You can also add a module as a namespace, all generated files will be put in the proper subfolders and modules by using the --module option.

As an example:

rails g operation User --module Admin

This will generate the following operations:

• app/operations/admin/user/load.rb
• app/operations/admin/user/create.rb
• app/operations/admin/user/update.rb
• app/operations/admin/user/destroy.rb

These operations will be namespaced in the Admin module, e.g. app/operations/admin/user/load.rb will define Operations::Admin::User::Load.

It will also generate the controller app/controllers/admin/users_controller.rb and the following empty view files:

• app/views/admin/users/index.html.haml
• app/views/admin/users/show.html.haml
• app/views/admin/users/new.html.haml
• app/views/admin/users/edit.html.haml

Both lower- and uppercase will generate the same files (i.e. --module Admin and --module admin are equal).

You can even nest the generated files deeper, --module Admin::Foo and --module admin/foo will both work.

Of course, at this point, the operations will need some adaptions, especially the parameter schemas, and the controllers need the logic for the success and failure cases, as this depends on your application.

Caveats

Eager loading in development mode

Eager loading operation classes containing models with nested models or operations can be very slow in performance. In production mode, the same process is very fast and not an issue at all. To work around this problem, make sure you exclude your operation classes (i.e. app/operations) in your config.eager_load_paths of development.rb. Make sure not to touch this setting in production mode though.

Contributors

This Gem is heavily inspired by the trailblazer Gem which provides a wonderful, high-level architecture for Rails – beyond just operations. Be sure to check this out when trying to decide on an alternative Rails architecture.

Copyright

Copyright © 2017 - 2024 Sitrox. See LICENSE for further details.