Ruby On Rails

We perform simple queries using dynamic finder and for commonly used query logic we use named scope.
<br /> User.find_all_by_user_name_and_password(user_name, password)<br /> # SELECT * FROM users WHERE user_name = user_name AND password = password</p> <p>named_scope :active, :conditions => { :status => true}</p> <p>User.active<br /> # SELECT * FROM users WHERE status=1<br />

but we cant chain query conditions when using these dynamic finders.

With the addition of dynamic scopes, we can now have a way to both quickly specify query logic and chain further conditions.

<br /> User.scoped_by_user_name_and_password(user_name, password).find(:all, :limit => 3)<br /> #=> SELECT * FROM users WHERE user_name = user_name AND password = password LIMIT 3</p> <p>User.scoped_by_user_name(user_name).scoped_by_password(password)<br /> #=> SELECT * FROM users WHERE user_name = user_name AND password = password</p> <p>User.scoped_by_user_name(user_name).scoped_by_password(password).scoped_by_status(true)<br /> #=> SELECT * FROM users WHERE user_name = user_name AND password = password AND status=1<br />
We can now use class methods like scoped_by_user_name(user_name) and scoped_by_user_name_and_password(user_name, password) that will use the scoped method with attributes you supply.

Ruby on Rails and Merb team decided to