Active Record Reflection

Reflection enables the ability to examine the associations and aggregations of Active Record classes and objects. This information, for example, can be used in a form builder that takes an Active Record object and creates input fields for all of the attributes depending on their type and displays the associations to other objects.

MacroReflection class has info for AggregateReflection and AssociationReflection classes.

Methods

Instance Public methods

reflect_on_aggregation(aggregation)

Returns the AggregateReflection object for the named aggregation (use the symbol).

Account.reflect_on_aggregation(:balance) # => the balance AggregateReflection
📝 Source code 
# File activerecord/lib/active_record/reflection.rb, line 69
      def reflect_on_aggregation(aggregation)
        aggregate_reflections[aggregation.to_s]
      end
🔎 See on GitHub

reflect_on_all_aggregations()

Returns an array of AggregateReflection objects for all the aggregations in the class.

📝 Source code 
# File activerecord/lib/active_record/reflection.rb, line 61
      def reflect_on_all_aggregations
        aggregate_reflections.values
      end
🔎 See on GitHub

reflect_on_all_associations(macro = nil)

Returns an array of AssociationReflection objects for all the associations in the class. If you only want to reflect on a certain association type, pass in the symbol (:has_many, :has_one, :belongs_to) as the first parameter.

Example:

Account.reflect_on_all_associations             # returns an array of all associations
Account.reflect_on_all_associations(:has_many)  # returns an array of all has_many associations
📝 Source code 
# File activerecord/lib/active_record/reflection.rb, line 106
      def reflect_on_all_associations(macro = nil)
        association_reflections = reflections.values
        association_reflections.select! { |reflection| reflection.macro == macro } if macro
        association_reflections
      end
🔎 See on GitHub

reflect_on_all_autosave_associations()

Returns an array of AssociationReflection objects for all associations which have :autosave enabled.

📝 Source code 
# File activerecord/lib/active_record/reflection.rb, line 126
      def reflect_on_all_autosave_associations
        reflections.values.select { |reflection| reflection.options[:autosave] }
      end
🔎 See on GitHub

reflect_on_association(association)

Returns the AssociationReflection object for the association (use the symbol).

Account.reflect_on_association(:owner)             # returns the owner AssociationReflection
Invoice.reflect_on_association(:line_items).macro  # returns :has_many
📝 Source code 
# File activerecord/lib/active_record/reflection.rb, line 117
      def reflect_on_association(association)
        reflections[association.to_s]
      end
🔎 See on GitHub

reflections()

Returns a Hash of name of the reflection as the key and an AssociationReflection as the value.

Account.reflections # => {"balance" => AggregateReflection}
📝 Source code 
# File activerecord/lib/active_record/reflection.rb, line 77
      def reflections
        @__reflections ||= begin
          ref = {}

          _reflections.each do |name, reflection|
            parent_reflection = reflection.parent_reflection

            if parent_reflection
              parent_name = parent_reflection.name
              ref[parent_name.to_s] = parent_reflection
            else
              ref[name] = reflection
            end
          end

          ref
        end
      end
🔎 See on GitHub