Module: ActiveRecord::Reflection::ClassMethods

Defined in:
lib/active_record/reflection.rb

Overview

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.

Instance Method Summary collapse

Instance Method Details

#create_reflection(macro, name, scope, options, active_record) ⇒ Object


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# File 'lib/active_record/reflection.rb', line 20

def create_reflection(macro, name, scope, options, active_record)
  case macro
  when :has_many, :belongs_to, :has_one, :has_and_belongs_to_many
    klass = options[:through] ? ThroughReflection : AssociationReflection
    reflection = klass.new(macro, name, scope, options, active_record)
  when :composed_of
    reflection = AggregateReflection.new(macro, name, scope, options, active_record)
  end

  self.reflections = self.reflections.merge(name => reflection)
  reflection
end

#reflect_on_aggregation(aggregation) ⇒ Object

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

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

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# File 'lib/active_record/reflection.rb', line 42

def reflect_on_aggregation(aggregation)
  reflection = reflections[aggregation]
  reflection if reflection.is_a?(AggregateReflection)
end

#reflect_on_all_aggregationsObject

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


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# File 'lib/active_record/reflection.rb', line 34

def reflect_on_all_aggregations
  reflections.values.grep(AggregateReflection)
end

#reflect_on_all_associations(macro = nil) ⇒ Object

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

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# File 'lib/active_record/reflection.rb', line 57

def reflect_on_all_associations(macro = nil)
  association_reflections = reflections.values.grep(AssociationReflection)
  macro ? association_reflections.select { |reflection| reflection.macro == macro } : association_reflections
end

#reflect_on_all_autosave_associationsObject

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


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# File 'lib/active_record/reflection.rb', line 73

def reflect_on_all_autosave_associations
  reflections.values.select { |reflection| reflection.options[:autosave] }
end

#reflect_on_association(association) ⇒ Object

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

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# File 'lib/active_record/reflection.rb', line 67

def reflect_on_association(association)
  reflection = reflections[association]
  reflection if reflection.is_a?(AssociationReflection)
end