DRY your scopes

I encountered a pattern today that I would like to share:

	class User < ActiveRecord::Base
	STATUS = { :active => 1, :inactive => 2, :pending => 3, :announce => 4, :curator => 5 }
	scope :active, where("status = #{STATUS[:active]}")
	scope :inactive, where("status = #{STATUS[:inactive]}")
	scope :pending, where("status = #{STATUS[:pending]}")
	scope :announce, where("status = #{STATUS[:announce]}")
	end

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user.rb

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There is no justification to write such a code in ruby (or in any language)
ActiveRecord 3 with ARel does not defer class singleton methods from scopes and in my opinion they are more readable.
We could write the same functionality with:

	class User < ActiveRecord::Base
	STATUS = { :active => 1, :inactive => 2, :pending => 3, :announce => 4, :curator => 5 }
	def self.active; where(:status => STATUS[:active]); end
	def self.inactive; where(:status => STATUS[:inactive]); end
	def self.pending; where(:status => STATUS[:pending]); end
	def self.announce; where(:status => STATUS[:announce]); end
	end

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user.rb

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Now, the path is short to go to:

	class User < ActiveRecord::Base
	STATUS = { :active => 1, :inactive => 2, :pending => 3, :announce => 4, :curator => 5 }
	STATUS.each do |k, v|
	define_singleton_method(k) do
	where(:status => v)
	end
	end
	end

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user.rb

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I like it – do you?

We didn’t only clean the code.
We did much more – every new status in the STATUS list will effortlessly represented with a matching method.

For instance :curator key which had no scope in the original version is now represented with the User.curator method.

DRY is not (just) about aesthetics. DRY is about maintainability and simplicity.