Composing several named_scopes into another

Rails
1

I have several named scopes in my app. Some patterns are
used commonly. For example:

Article.published_in(publication).published.viewable_by(current_user).included_in_index

Since this pattern is repeated, I’d like to be able to have a
named_scope that embeds this pattern.
I’ve tried defining a named_scope in terms of several changed
named_scopes but that doesn’t work.

Is there a way to do this? Something like:

named_scope :permitted, :lambda {|user, publication|
published_in(publication).published.viewable_by(user).included_in_index
}

I supposed a class method would be the natural alternative, but am
curious if there is indeed a way
to compose named_scopes.

Cheers, --Kip

2

Kip Cole wrote:

I have several named scopes in my app. Some patterns are
used commonly. For example:

Article.published_in(publication).published.viewable_by(current_user).included_in_index

Since this pattern is repeated, I’d like to be able to have a
named_scope that embeds this pattern.
I’ve tried defining a named_scope in terms of several changed
named_scopes but that doesn’t work.

Is there a way to do this? Something like:

named_scope :permitted, :lambda {|user, publication|
published_in(publication).published.viewable_by(user).included_in_index
}

I supposed a class method would be the natural alternative, but am
curious if there is indeed a way
to compose named_scopes.

Cheers, --Kip

It’s not possible out of the box, but check out the patches posted in
this discussion:
http://rails.lighthouseapp.com/projects/8994/tickets/57-through-option-for-named_scope

It gives you a :through option for named_scope. So you can do:

named_scope :all, :conditions => [‘deleted = ?’, false]
named_scope :active, :conditions => [‘active = ?’, true], :through =>
:all