Adi Pradhan

Rails used an ORM (Object Relational Mapper) called Active Record that has a lot of cool features, one of these is scopes.

A scope is essentially a SQL WHERE clause and it is written as below

class Book < ActiveRecord::Base
	scope :recent, -> { where('finished_on > ?',2.days.ago)}
end

so running Book.recent in rails console or in your app will give you all Books with the recent value being within the last two days.

But what is a scope? If you think of each row in the Books table as an instance of the Book class. Then the scope is simply a class method. So writing the scope as below is almost equivalent

class Book < ActiveRecord::Base
	def self.recent
		where('finished_on > ?',2.days.ago)
	end
end

almost… there are a few subtle differences