Comments on: How to alias and create a new named scope out of existing ones

By: scragz

scragz — Mon, 07 Feb 2011 03:17:43 +0000

I wanted to just make some simple aliases like alias_method so I whipped this up:

module ActiveRecord
class Base
def self.alias_named_scope(alias_scope, original_scope)
named_scope alias_scope, lambda { self.send(original_scope).scope(:find) }
end
end
end

By: David Ongaro

David Ongaro — Fri, 04 Jun 2010 12:05:38 +0000

Nice. Even though just defining a method like

def self.has_moo_and_foo
has_moo. has_foo
end

also works, I find the named_scope syntax more appealing, because one can scan the named scopes in one sight. (And they also show up in Fu.scopes).

When you define the scopes in the right order, the lambda gets superflous though. So

named_scope :has_moo_and_foo, has_moo.has_foo.scope(:find)

is enough. But default_scope conditions are duplicated in this way (with or without lambda). Even though this doesn’t might hurt it seems to be saver to just exclude them:

named_scope :has_moo_and_foo, with_exclusive_scope { has_moo.has_foo.scope(:find) }

By: Michael Thompson

Michael Thompson — Fri, 18 Sep 2009 08:09:53 +0000

Thanks, this was useful. I had a bunch of anonymous named scopes I needed to chain together, but with OR, rather than AND. It was simple to create a new scope using the collection of #scope(:find)[:conditions] joined with ” OR “.