Betternestedset talk - Apr 2007 - better nested set and :through

Hello all,

It''s been a while since i''ve been doing any rails development,
so i''m a
bit rusty.  Having found this:
http://opensource.symetrie.com/api/better_nested_set/

it looks really interesting and useful for solving something i''m trying
to get working.

What i have (essentially) is the following models:

class Group < ActiveRecord::Base
        acts_as_nested_set
        has_many :memberships
        has_many :users, :through => :memberships
        belongs_to :owner, :class_name => "User"
end

class Membership < ActiveRecord::Base
        belongs_to :group
        belongs_to :user
end

class User < ActiveRecord::Base
        has_many :memberships
        has_many :groups, :through => :memberships

end



Now then, what i''d like to know is how do i go about finding all the
Users contained within a nested set?

for example:

admins = Group.find_by_name "admins"
admins.users # gives all users in the admins group.

and

admins.all_children # gives me all the groups

I thought the following methods sounded promising, but i get
NoMethodError''s from them:

admins.children.find_all_in_users
admins.children.find_in_users


Perhaps i''m going about this the wrong way or i''m missing a
more obvious
solution.  Can anyone shed some light on it?

Cheers,
-vince

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Hi,

Le 29 avr. 07, ? 14:54, Vincent AE Scott a ?crit :
> It''s been a while since i''ve been doing any rails
development, so i''m a
> bit rusty.  Having found this:
> http://opensource.symetrie.com/api/better_nested_set/
>
> it looks really interesting and useful for solving something i''m
trying
> to get working.
>
> What i have (essentially) is the following models:
>
> class Group < ActiveRecord::Base
>         acts_as_nested_set
>         has_many :memberships
>         has_many :users, :through => :memberships
>         belongs_to :owner, :class_name => "User"
> end
>
> class Membership < ActiveRecord::Base
>         belongs_to :group
>         belongs_to :user
> end
>
> class User < ActiveRecord::Base
>         has_many :memberships
>         has_many :groups, :through => :memberships
>
> end
>
> Now then, what i''d like to know is how do i go about finding all
the
> Users contained within a nested set?
>
> for example:
>
> admins = Group.find_by_name "admins"
> admins.users # gives all users in the admins group.
>
> and
>
> admins.all_children # gives me all the groups
>
> I thought the following methods sounded promising, but i get
> NoMethodError''s from them:
>
> admins.children.find_all_in_users
> admins.children.find_in_users
>
>
> Perhaps i''m going about this the wrong way or i''m missing
a more
> obvious
> solution.  Can anyone shed some light on it?
I think the problem you raise is more related to find and :through than 
to nested sets.
You should have a look on :include in find :

admins = Group.find_by_name ''admins'', :include =>
[{''memberships'' =>
''users''}]

then simply grab your users with

users = admins.inject([]){|u, a| u << a.users}.uniq


Jean-Christophe Michel
--
symetrie.com

Better Nested Set for rails:
http://opensource.symetrie.com/trac/better_nested_set