# module ActiveRecord::Reflection::ClassMethods

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.

### Public Instance Methods

reflect_on_aggregation(aggregation) click to toggle source

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

    Account.reflect_on_aggregation(:balance) # => the balance AggregateReflection

    # File lib/active_record/reflection.rb, line 63
    def reflect_on_aggregation(aggregation)
      aggregate_reflections[aggregation.to_s]
    end

reflect_on_all_aggregations() click to toggle source

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

    # File lib/active_record/reflection.rb, line 55
    def reflect_on_all_aggregations
      aggregate_reflections.values
    end

reflect_on_all_associations(macro = nil) click to toggle source

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

    # File lib/active_record/reflection.rb, line 100
    def reflect_on_all_associations(macro = nil)
      association_reflections = reflections.values
      association_reflections.select! { |reflection| reflection.macro == macro } if macro
      association_reflections
    end

reflect_on_all_autosave_associations() click to toggle source

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

    # File lib/active_record/reflection.rb, line 120
    def reflect_on_all_autosave_associations
      reflections.values.select { |reflection| reflection.options[:autosave] }
    end

reflect_on_association(association) click to toggle source

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

    # File lib/active_record/reflection.rb, line 111
    def reflect_on_association(association)
      reflections[association.to_s]
    end

reflections() click to toggle source

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

    Account.reflections # => {"balance" => AggregateReflection}

    # File lib/active_record/reflection.rb, line 71
    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