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, options, active_record) ⇒ Object 



15
16
17
18
19
20
21
22
23
24
25
 
# File 'lib/active_record/reflection.rb', line 15

def create_reflection(macro, name, 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, options, active_record)
    when :composed_of
      reflection = AggregateReflection.new(macro, name, options, active_record)
  end
  write_inheritable_hash :reflections, 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



46
47
48
 
# File 'lib/active_record/reflection.rb', line 46

def reflect_on_aggregation(aggregation)
  reflections[aggregation].is_a?(AggregateReflection) ? reflections[aggregation] : nil
end

#reflect_on_all_aggregations ⇒ Object

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



38
39
40
 
# File 'lib/active_record/reflection.rb', line 38

def reflect_on_all_aggregations
  reflections.values.select { |reflection| reflection.is_a?(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



60
61
62
63
 
# File 'lib/active_record/reflection.rb', line 60

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

#reflect_on_all_autosave_associations ⇒ Object

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



75
76
77
 
# File 'lib/active_record/reflection.rb', line 75

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



70
71
72
 
# File 'lib/active_record/reflection.rb', line 70

def reflect_on_association(association)
  reflections[association].is_a?(AssociationReflection) ? reflections[association] : nil
end

#reflections ⇒ Object

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

Invoice.reflections
Account.reflections



33
34
35
 
# File 'lib/active_record/reflection.rb', line 33

def reflections
  read_inheritable_attribute(:reflections) || write_inheritable_attribute(:reflections, {})
end