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ActiveRecord::Reflection::ClassMethods

Reflection enables to interrogate Active Record classes and objects about their associations and aggregations. This information can, for example, 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

create_reflection(macro, name, options, active_record) click to toggle source
    # File lib/active_record/reflection.rb, line 15
15:       def create_reflection(macro, name, options, active_record)
16:         case macro
17:           when :has_many, :belongs_to, :has_one, :has_and_belongs_to_many
18:             klass = options[:through] ? ThroughReflection : AssociationReflection
19:             reflection = klass.new(macro, name, options, active_record)
20:           when :composed_of
21:             reflection = AggregateReflection.new(macro, name, options, active_record)
22:         end
23:         write_inheritable_hash :reflections, name => reflection
24:         reflection
25:       end
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 46
46:       def reflect_on_aggregation(aggregation)
47:         reflections[aggregation].is_a?(AggregateReflection) ? reflections[aggregation] : nil
48:       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 38
38:       def reflect_on_all_aggregations
39:         reflections.values.select { |reflection| reflection.is_a?(AggregateReflection) }
40:       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 60
60:       def reflect_on_all_associations(macro = nil)
61:         association_reflections = reflections.values.select { |reflection| reflection.is_a?(AssociationReflection) }
62:         macro ? association_reflections.select { |reflection| reflection.macro == macro } : association_reflections
63:       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 75
75:       def reflect_on_all_autosave_associations
76:         reflections.values.select { |reflection| reflection.options[:autosave] }
77:       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 70
70:       def reflect_on_association(association)
71:         reflections[association].is_a?(AssociationReflection) ? reflections[association] : nil
72:       end
reflections() click to toggle source

Returns a hash containing all AssociationReflection objects for the current class. Example:

  Invoice.reflections
  Account.reflections
    # File lib/active_record/reflection.rb, line 33
33:       def reflections
34:         read_inheritable_attribute(:reflections) || write_inheritable_attribute(:reflections, {})
35:       end

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