method_access.rb

module Hashie
  module Extensions
    # MethodReader allows you to access keys of the hash
    # via method calls. This gives you an OStruct like way
    # to access your hash's keys. It will recognize keys
    # either as strings or symbols.
    #
    # Note that while nil keys will be returned as nil,
    # undefined keys will raise NoMethodErrors. Also note that
    # #respond_to? has been patched to appropriately recognize
    # key methods.
    #
    # @example
    #   class User < Hash
    #     include Hashie::Extensions::MethodReader
    #   end
    #
    #   user = User.new
    #   user['first_name'] = 'Michael'
    #   user.first_name # => 'Michael'
    #
    #   user[:last_name] = 'Bleigh'
    #   user.last_name # => 'Bleigh'
    #
    #   user[:birthday] = nil
    #   user.birthday # => nil
    #
    #   user.not_declared # => NoMethodError
    module MethodReader
      def respond_to_missing?(name, include_private = false)
        return true if key?(name.to_s) || key?(name.to_sym)
        super
      end

      def method_missing(name, *args)
        if key?(name)
          self[name]
        else
          sname = name.to_s
          if key?(sname)
            self[sname]
          elsif sname[-1] == '?'
            kname = sname[0..-2]
            key?(kname) || key?(kname.to_sym)
          else
            super
          end
        end
      end
    end

    # MethodWriter gives you #key_name= shortcuts for
    # writing to your hash. Keys are written as strings,
    # override #convert_key if you would like to have symbols
    # or something else.
    #
    # Note that MethodWriter also overrides #respond_to such
    # that any #method_name= will respond appropriately as true.
    #
    # @example
    #   class MyHash < Hash
    #     include Hashie::Extensions::MethodWriter
    #   end
    #
    #   h = MyHash.new
    #   h.awesome = 'sauce'
    #   h['awesome'] # => 'sauce'
    #
    module MethodWriter
      def respond_to_missing?(name, include_private = false)
        return true if name.to_s =~ /=$/
        super
      end

      def method_missing(name, *args)
        if args.size == 1 && name.to_s =~ /(.*)=$/
          return self[convert_key(Regexp.last_match[1])] = args.first
        end

        super
      end

      def convert_key(key)
        key.to_s
      end
    end

    # MethodQuery gives you the ability to check for the truthiness
    # of a key via method calls. Note that it will return false if
    # the key is set to a non-truthful value, not if the key isn't
    # set at all. Use #key? for checking if a key has been set.
    #
    # MethodQuery will check against both string and symbol names
    # of the method for existing keys. It also patches #respond_to
    # to appropriately detect the query methods.
    #
    # @example
    #   class MyHash < Hash
    #     include Hashie::Extensions::MethodQuery
    #   end
    #
    #   h = MyHash.new
    #   h['abc'] = 123
    #   h.abc? # => true
    #   h['def'] = nil
    #   h.def? # => false
    #   h.hji? # => NoMethodError
    module MethodQuery
      def respond_to_missing?(name, include_private = false)
        if query_method?(name) && indifferent_key?(key_from_query_method(name))
          true
        else
          super
        end
      end

      def method_missing(name, *args)
        return super unless args.empty?

        if query_method?(name)
          key = key_from_query_method(name)
          if indifferent_key?(key)
            !!(self[key] || self[key.to_sym])
          else
            super
          end
        else
          super
        end
      end

      private

      def indifferent_key?(name)
        name = name.to_s
        key?(name) || key?(name.to_sym)
      end

      def key_from_query_method(query_method)
        query_method.to_s[0..-2]
      end

      def query_method?(name)
        name.to_s.end_with?('?')
      end
    end

    # A macro module that will automatically include MethodReader,
    # MethodWriter, and MethodQuery, giving you the ability to read,
    # write, and query keys in a hash using method call shortcuts.
    module MethodAccess
      def self.included(base)
        [MethodReader, MethodWriter, MethodQuery].each do |mod|
          base.send :include, mod
        end
      end
    end

    # A module shared between MethodOverridingWriter and MethodOverridingInitializer
    # to contained shared logic. This module aids in redefining existing hash methods.
    module RedefineMethod
      protected

      def method?(name)
        methods.map(&:to_s).include?(name)
      end

      def redefine_method(method_name)
        eigenclass = class << self; self; end
        eigenclass.__send__(:alias_method, "__#{method_name}", method_name)
        eigenclass.__send__(:define_method, method_name, -> { self[method_name] })
      end
    end

    # MethodOverridingWriter gives you #key_name= shortcuts for
    # writing to your hash. It allows methods to be overridden by
    # #key_name= shortcuts and aliases those methods with two
    # leading underscores.
    #
    # Keys are written as strings. Override #convert_key if you
    # would like to have symbols or something else.
    #
    # Note that MethodOverridingWriter also overrides
    # #respond_to_missing? such that any #method_name= will respond
    # appropriately as true.
    #
    # @example
    #   class MyHash < Hash
    #     include Hashie::Extensions::MethodOverridingWriter
    #   end
    #
    #   h = MyHash.new
    #   h.awesome = 'sauce'
    #   h['awesome'] # => 'sauce'
    #   h.zip = 'a-dee-doo-dah'
    #   h.zip # => 'a-dee-doo-dah'
    #   h.__zip # => [[['awesome', 'sauce'], ['zip', 'a-dee-doo-dah']]]
    #
    module MethodOverridingWriter
      include RedefineMethod

      def convert_key(key)
        key.to_s
      end

      def method_missing(name, *args)
        if args.size == 1 && name.to_s =~ /(.*)=$/
          key = Regexp.last_match[1]
          redefine_method(key) if method?(key) && !already_overridden?(key)
          return self[convert_key(key)] = args.first
        end

        super
      end

      def respond_to_missing?(name, include_private = false)
        return true if name.to_s.end_with?('=')
        super
      end

      protected

      def already_overridden?(name)
        method?("__#{name}")
      end
    end

    # A macro module that will automatically include MethodReader,
    # MethodOverridingWriter, and MethodQuery, giving you the ability
    # to read, write, and query keys in a hash using method call
    # shortcuts that can override object methods. Any overridden
    # object method is automatically aliased with two leading
    # underscores.
    module MethodAccessWithOverride
      def self.included(base)
        [MethodReader, MethodOverridingWriter,
         MethodQuery, MethodOverridingInitializer].each do |mod|
          base.send :include, mod
        end
      end
    end

    # MethodOverridingInitializer allows you to override default hash
    # methods when passing in values from an existing hash. The overridden
    # methods are aliased with two leading underscores.
    #
    # @example
    #   class MyHash < Hash
    #     include Hashie::Extensions::MethodOverridingInitializer
    #   end
    #
    #   h = MyHash.new(zip: 'a-dee-doo-dah')
    #   h.zip # => 'a-dee-doo-dah'
    #   h.__zip # => [[['zip', 'a-dee-doo-dah']]]
    module MethodOverridingInitializer
      include RedefineMethod

      def initialize(hash = {})
        hash.each do |key, value|
          skey = key.to_s
          redefine_method(skey) if method?(skey)
          self[skey] = value
        end
      end
    end
  end
end