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# ActiveModel::Dirty does not support associations but it's sometime it'd be useful
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# so you could ask like this
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# @user.role_ids_was
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#
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# This concern can be used exactly for this. Note that it does not detect changes to
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# associated object but just change of the collection itself.
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#
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# Also note one difference to built-in attribute dirty cache for new records. With
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# this concern we don't wait on saving the record which results in following behavior
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# @user = User.new
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# @user.role_ids = [8]
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# @user.role_ids = [8, 9]
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# @user.role_ids_was # => [8]
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module DirtyAssociations
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extend ActiveSupport::Concern
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module ClassMethods
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# usage:
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# class Model
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# dirty_has_many_associations :organizations, :locations
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def dirty_has_many_associations(*args)
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args.each do |association|
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association_ids = association.to_s.singularize + '_ids'
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# result for :organizations
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# def organization_ids_with_change_detection=(organizations)
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# organizations ||= []
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# @organization_ids_changed = organizations.uniq.select(&:present?).map(&:to_i).sort != organization_ids.sort
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# @organization_ids_was = organization_ids.clone
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# self.organization_ids_without_change_detection = organizations
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# end
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define_method "#{association_ids}_with_change_detection=" do |collection|
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collection ||= [] # in API, #{association}_ids is converted to nil if user sent empty array
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instance_variable_set("@#{association_ids}_changed", collection.uniq.select(&:present?).map(&:to_i).sort != self.send(association_ids).sort)
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instance_variable_set("@#{association_ids}_was", self.send(association_ids).clone)
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self.send("#{association_ids}_without_change_detection=", collection)
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end
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alias_method_chain("#{association_ids}=", :change_detection)
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# result for :organizations
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# def organization_ids_changed?
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# @organization_ids_changed
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# end
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define_method "#{association_ids}_changed?" do
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instance_variable_get("@#{association_ids}_changed")
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end
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# result for :organizations
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# def organization_ids_was
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# @organization_ids_was ||= organization_ids
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# end
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define_method "#{association_ids}_was" do
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value = instance_variable_get("@#{association_ids}_was")
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if value.nil?
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instance_variable_set("@#{association_ids}_was", self.send(association_ids))
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else
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value
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end
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end
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end
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end
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end
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end
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