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Jeff Blasius

2009-Dec-01 16:45 UTC

named_scope with at least one association

How would I write a named_scope that checks if the parent has at least
one associated child?

For example,
class Post < ActiveRecord::Base
  has many :comments

  named_scope :commented_on, :conditions => "comments.count > 0"


class Comment < ActiveRecord::Base
  belongs_to :post



Thanks,
            jeff

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tommy xiao

2009-Dec-02 11:31 UTC

head link

Re: named_scope with at least one association

i think use named_scope is not elegant way. use class method? no idea.you
can give me your sample proj.i can test this way.

2009/12/2 Jeff Blasius
<jeff.blasius-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> How would I write a named_scope that checks if the parent has at least
> one associated child?
>
> For example,
> class Post < ActiveRecord::Base
>  has many :comments
>
>  named_scope :commented_on, :conditions => "comments.count >
0"
>
>
> class Comment < ActiveRecord::Base
>  belongs_to :post
>
>
>
> Thanks,
>            jeff
>
> --
>
> You received this message because you are subscribed to the Google Groups
> "Ruby on Rails: Talk" group.
> To post to this group, send email to
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> To unsubscribe from this group, send email to
>
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> .
> For more options, visit this group at
> http://groups.google.com/group/rubyonrails-talk?hl=en.
>
>
>

-- 
tommy xiao
E-mail: xiaods(AT)gmail.com

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tommy xiao

2009-Dec-02 11:49 UTC

head link

Re: named_scope with at least one association

i got it.
reference this url:
http://refactormycode.com/codes/209-rails-has_many-count

sample code:

class User
  has_many :messages do
    def by_type(type, options={})
      options[:count_only] ||= false
      messages = find(:all, :conditions => [ ''type = ?'',
type ])
      options[:count_only] ? messages.size : messages
    end
  end
end


OPTION 1: without helper in view

<h1>Messages:</h1>

<ul>
  <li>Industry Expert: <%=
current_user.messages.by_type(''Industry
Expert'', :count_only => true) -%></li>
  <li>Media:           <%=
current_user.messages.by_type(''Media'',
     :count_only => true) -%></li>
  <li>PR:              <%=
current_user.messages.by_type(''PR'',
     :count_only => true) -%></li>
</ul>









2009/12/2 tommy xiao <xiaods-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> i think use named_scope is not elegant way. use class method? no idea.you
> can give me your sample proj.i can test this way.
>
> 2009/12/2 Jeff Blasius
<jeff.blasius-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>
> How would I write a named_scope that checks if the parent has at least
>> one associated child?
>>
>> For example,
>> class Post < ActiveRecord::Base
>>  has many :comments
>>
>>  named_scope :commented_on, :conditions => "comments.count >
0"
>>
>>
>> class Comment < ActiveRecord::Base
>>  belongs_to :post
>>
>>
>>
>> Thanks,
>>            jeff
>>
>> --
>>
>> You received this message because you are subscribed to the Google
Groups
>> "Ruby on Rails: Talk" group.
>> To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
>> To unsubscribe from this group, send email to
>>
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org<rubyonrails-talk%2Bunsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org>
>> .
>> For more options, visit this group at
>> http://groups.google.com/group/rubyonrails-talk?hl=en.
>>
>>
>>
>
>
> --
> tommy xiao
> E-mail: xiaods(AT)gmail.com
>


-- 
tommy xiao
E-mail: xiaods(AT)gmail.com

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Pedro Del Gallego

2009-Dec-03 09:23 UTC

head link

Re: named_scope with at least one association

> How would I write a named_scope that checks if the parent has at least
> one associated child?
First, its better to describe the problem a liitle bit, what I
undestand if you want to find only the post that have post, Isnt it ?

Look this example : I wrote by heart, so probably you will have some errors
describe Post, "find methods" do
  context "find recent comments" do
    before :each do
      (1..10).each {|n|   Comment.create(valid_comment_attributes) }
      post = Post.create! valid_post_attributes
    end

    it "should not return post with no comments" do
      Post.commented_posts.should_not include post
    end
  end
end

So you need to include the comments, but the normal :include =>
:comments make by default I think make LEFT OUTER  join, and what you
need is a INNER JOIN, so you can specify that in the :join parameter.

named_scope :commented_posts, lambda { {:joins  => ''INNER JOIN
comments ON comments.post_id = posts.id''}}

its that enough , maybe, but you will discover after a while a problem
some problems like, that you have repeated_posts, and then you should
and remove the duplication in another named_scope, or in a the same one

it "should not have repeated post" do
  post = Comment.create(valid_comment_attributes :post=>Post.first)
  Post.commented_posts.should have_exactly(10).posts
end








> For example,
> class Post < ActiveRecord::Base
>  has many :comments
>
>  named_scope :commented_on, :conditions => "comments.count >
0"
>
>
> class Comment < ActiveRecord::Base
>  belongs_to :post
>
>
>
> Thanks,
>            jeff
>
> --
>
> You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
> To post to this group, send email to
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rubyonrails-talk+unsubscribe@googlegroups.com.
> For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.
>
>
>


-- 
-------------------------------------
Pedro Del Gallego

Email              :   pedro.delgallego-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org

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Rails - Dec 2009 - named_scope with at least one association

named_scope with at least one association

Re: named_scope with at least one association

Re: named_scope with at least one association

Re: named_scope with at least one association