Module | ActiveRecord::Reflection::ClassMethods |
In: |
vendor/rails/activerecord/lib/active_record/reflection.rb
|
Reflection allows you to interrogate Active Record classes and objects about their associations and aggregations. This information can, for example, be used in a form builder that took an Active Record object and created input fields for all of the attributes depending on their type and displayed the associations to other objects.
You can find the interface for the AggregateReflection and AssociationReflection classes in the abstract MacroReflection class.
# File vendor/rails/activerecord/lib/active_record/reflection.rb, line 13 13: def create_reflection(macro, name, options, active_record) 14: case macro 15: when :has_many, :belongs_to, :has_one, :has_and_belongs_to_many 16: reflection = AssociationReflection.new(macro, name, options, active_record) 17: when :composed_of 18: reflection = AggregateReflection.new(macro, name, options, active_record) 19: end 20: write_inheritable_hash :reflections, name => reflection 21: reflection 22: end
Returns the AggregateReflection object for the named aggregation (use the symbol). Example:
Account.reflect_on_aggregation(:balance) # returns the balance AggregateReflection
# File vendor/rails/activerecord/lib/active_record/reflection.rb, line 43 43: def reflect_on_aggregation(aggregation) 44: reflections[aggregation].is_a?(AggregateReflection) ? reflections[aggregation] : nil 45: end
Returns an array of AggregateReflection objects for all the aggregations in the class.
# File vendor/rails/activerecord/lib/active_record/reflection.rb, line 35 35: def reflect_on_all_aggregations 36: reflections.values.select { |reflection| reflection.is_a?(AggregateReflection) } 37: end
Returns an array of AssociationReflection objects for all the aggregations in the class. If you only want to reflect on a certain association type, pass in the symbol (:has_many, :has_one, :belongs_to) for that 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 vendor/rails/activerecord/lib/active_record/reflection.rb, line 54 54: def reflect_on_all_associations(macro = nil) 55: association_reflections = reflections.values.select { |reflection| reflection.is_a?(AssociationReflection) } 56: macro ? association_reflections.select { |reflection| reflection.macro == macro } : association_reflections 57: end
Returns the AssociationReflection object for the named aggregation (use the symbol). Example:
Account.reflect_on_association(:owner) # returns the owner AssociationReflection Invoice.reflect_on_association(:line_items).macro # returns :has_many
# File vendor/rails/activerecord/lib/active_record/reflection.rb, line 64 64: def reflect_on_association(association) 65: reflections[association].is_a?(AssociationReflection) ? reflections[association] : nil 66: end
Returns a hash containing all AssociationReflection objects for the current class Example:
Invoice.reflections Account.reflections
# File vendor/rails/activerecord/lib/active_record/reflection.rb, line 30 30: def reflections 31: read_inheritable_attribute(:reflections) || write_inheritable_attribute(:reflections, {}) 32: end