Use this macro in your model to set a default scope for all operations on the model.
class Article < ActiveRecord::Base
default_scope where(:published => true)
end
Article.all # => SELECT * FROM articles WHERE published = true
The default_scope is also applied while creating/building a record. It is not applied while updating a record.
Article.new.published # => true Article.create.published # => true
You can also use default_scope with a block, in order to have it lazily evaluated:
class Article < ActiveRecord::Base
default_scope { where(:published_at => Time.now - 1.week) }
end
(You can also pass any object which responds to call to the default_scope macro, and it will be called when building the default scope.)
If you use multiple default_scope declarations in your model then they will be merged together:
class Article < ActiveRecord::Base
default_scope where(:published => true)
default_scope where(:rating => 'G')
end
Article.all # => SELECT * FROM articles WHERE published = true AND rating = 'G'
This is also the case with inheritance and module includes where the parent or module defines a default_scope and the child or including class defines a second one.
If you need to do more complex things with a default scope, you can alternatively define it as a class method:
class Article < ActiveRecord::Base
def self.default_scope
# Should return a scope, you can call 'super' here etc.
end
end
The ignore_default_scope flag is used to prevent an infinite recursion situation where a default scope references a scope which has a default scope which references a scope...