Add simple option for auto-generated timestamps

README.md

@@ -20,6 +20,7 @@
   - [Extending AASM](#extending-aasm)
   - [ActiveRecord](#activerecord)
   - [Bang events](#bang-events)
+  - [Timestamps](#timestamps)
   - [ActiveRecord enums](#activerecord-enums)
   - [Sequel](#sequel)
   - [Dynamoid](#dynamoid)
@@ -777,6 +778,37 @@ job.aasm_state = :running # => raises AASM::NoDirectAssignmentError
 job.aasm_state # => 'sleeping'
 ```
 
+### Timestamps
+
+You can tell _AASM_ to try to write a timestamp whenever a new state is entered.
+If `timestamps: true` is set, _AASM_ will look for a field named like the new state plus `_at` and try to fill it:
+
+```ruby
+class Job < ActiveRecord::Base
+  include AASM
+
+  aasm timestamps: true do
+    state :sleeping, initial: true
+    state :running
+
+    event :run do
+      transitions from: :sleeping, to: :running
+    end
+  end
+end
+```
+
+resulting in this:
+
+```ruby
+job = Job.create
+job.running_at # => nil
+job.run!
+job.running_at # => 2020-02-20 20:00:00
+```
+
+Missing timestamp fields are silently ignored, so it is not necessary to have setters (such as ActiveRecord columns) for *all* states when using this option.
+
 #### ActiveRecord enums
 
 You can use

lib/aasm/base.rb

@@ -37,6 +37,9 @@ def initialize(klass, name, state_machine, options={}, &block)
       # string for a specific lock type i.e. FOR UPDATE NOWAIT
       configure :requires_lock, false
 
+      # automatically set `"#{state_name}_at" = ::Time.now` on state changes
+      configure :timestamps, false
+
       # set to true to forbid direct assignment of aasm_state column (in ActiveRecord)
       configure :no_direct_assignment, false
 
@@ -51,19 +54,12 @@ def initialize(klass, name, state_machine, options={}, &block)
       # Configure a logger, with default being a Logger to STDERR
       configure :logger, Logger.new(STDERR)
 
+      # setup timestamp-setting callback if enabled
+      setup_timestamps(@name)
+
       # make sure to raise an error if no_direct_assignment is enabled
       # and attribute is directly assigned though
-      aasm_name = @name
-
-      if @state_machine.config.no_direct_assignment
-        @klass.send(:define_method, "#{@state_machine.config.column}=") do |state_name|
-          if self.class.aasm(:"#{aasm_name}").state_machine.config.no_direct_assignment
-            raise AASM::NoDirectAssignmentError.new('direct assignment of AASM column has been disabled (see AASM configuration for this class)')
-          else
-            super(state_name)
-          end
-        end
-      end
+      setup_no_direct_assignment(@name)
     end
 
     # This method is both a getter and a setter
@@ -267,5 +263,28 @@ def skip_instance_level_validation(event, name, aasm_name, klass)
       end
     end
 
+    def setup_timestamps(aasm_name)
+      return unless @state_machine.config.timestamps
+
+      after_all_transitions do
+        if self.class.aasm(:"#{aasm_name}").state_machine.config.timestamps
+          ts_setter = "#{aasm.to_state}_at="
+          respond_to?(ts_setter) && send(ts_setter, ::Time.now)
+        end
+      end
+    end
+
+    def setup_no_direct_assignment(aasm_name)
+      return unless @state_machine.config.no_direct_assignment
+
+      @klass.send(:define_method, "#{@state_machine.config.column}=") do |state_name|
+        if self.class.aasm(:"#{aasm_name}").state_machine.config.no_direct_assignment
+          raise AASM::NoDirectAssignmentError.new('direct assignment of AASM column has been disabled (see AASM configuration for this class)')
+        else
+          super(state_name)
+        end
+      end
+    end
+
   end
 end

lib/aasm/configuration.rb

@@ -24,6 +24,9 @@ class Configuration
     # for ActiveRecord: use pessimistic locking
     attr_accessor :requires_lock
 
+    # automatically set `"#{state_name}_at" = ::Time.now` on state changes
+    attr_accessor :timestamps
+
     # forbid direct assignment in aasm_state column (in ActiveRecord)
     attr_accessor :no_direct_assignment
 

spec/database.rb

@@ -56,4 +56,9 @@
     t.string "state"
     t.string "some_string"
   end
+
+  ActiveRecord::Migration.create_table "timestamp_examples", :force => true do |t|
+    t.string "aasm_state"
+    t.datetime "opened_at"
+  end
 end

spec/models/active_record/timestamp_example.rb

@@ -0,0 +1,16 @@
+class TimestampExample < ActiveRecord::Base
+  include AASM
+
+  aasm column: :aasm_state, timestamps: true do
+    state :opened
+    state :closed
+
+    event :open do
+      transitions to: :opened
+    end
+
+    event :close do
+      transitions to: :closed
+    end
+  end
+end

spec/models/mongoid/timestamp_example_mongoid.rb

@@ -0,0 +1,20 @@
+class TimestampExampleMongoid
+  include Mongoid::Document
+  include AASM
+
+  field :status, type: String
+  field :opened_at, type: Time
+
+  aasm column: :status, timestamps: true do
+    state :opened
+    state :closed
+
+    event :open do
+      transitions to: :opened
+    end
+
+    event :close do
+      transitions to: :closed
+    end
+  end
+end

spec/models/timestamps_example.rb

@@ -0,0 +1,19 @@
+class TimestampsExample
+  include AASM
+
+  attr_accessor :opened_at
+  attr_reader :closed_at
+
+  aasm timestamps: true do
+    state :opened
+    state :closed
+
+    event :open do
+      transitions to: :opened
+    end
+
+    event :close do
+      transitions to: :closed
+    end
+  end
+end

spec/unit/persistence/active_record_persistence_spec.rb

@@ -770,4 +770,16 @@
       expect(example.complete!).to be_falsey
     end
   end
+
+  describe 'testing the timestamps option' do
+    let(:example) { TimestampExample.create! }
+
+    it 'should update existing timestamp columns' do
+      expect { example.open! }.to change { example.reload.opened_at }.from(nil).to(instance_of(::Time))
+    end
+
+    it 'should not fail if there is no corresponding timestamp column' do
+      expect { example.close! }.to change { example.reload.aasm_state }
+    end
+  end
 end

spec/unit/persistence/mongoid_persistence_spec.rb

@@ -161,5 +161,17 @@
       end
     end
 
+    describe 'testing the timestamps option' do
+      let(:example) { TimestampExampleMongoid.create }
+
+      it 'should update existing timestamp fields' do
+        expect { example.open! }.to change { example.reload.opened_at }.from(nil).to(instance_of(::Time))
+      end
+
+      it 'should not fail if there is no corresponding timestamp field' do
+        expect { example.close! }.to change { example.reload.status }
+      end
+    end
+
   end
 end

spec/unit/timestamps_spec.rb

@@ -0,0 +1,27 @@
+require 'spec_helper'
+
+describe 'timestamps option' do
+  it 'calls a timestamp setter based on the state name when entering a new state' do
+    object = TimestampsExample.new
+    expect { object.open }.to change { object.opened_at }.from(nil).to(instance_of(::Time))
+  end
+
+  it 'overwrites any previous timestamp if a state is entered repeatedly' do
+    object = TimestampsExample.new
+    object.opened_at = ::Time.new(2000, 1, 1)
+    expect { object.open }.to change { object.opened_at }
+  end
+
+  it 'does nothing if there is no setter matching the new state' do
+    object = TimestampsExample.new
+    expect { object.close }.not_to change { object.closed_at }
+  end
+
+  it 'can be turned off and on' do
+    object = TimestampsExample.new
+    object.class.aasm.state_machine.config.timestamps = false
+    expect { object.open }.not_to change { object.opened_at }
+    object.class.aasm.state_machine.config.timestamps = true
+    expect { object.open }.to change { object.opened_at }
+  end
+end