Rails - Jul 2006 - writing to many_to_many table

I have three tables.  users, posts, users_posts.  This last one is to 
mark a post as read.

How do I write to the users_post table?

Here''s what I have:

In model ''User_Post''
belongs_to :post
belongs_to :user

In post/view/show:
<%= link_to "Mark As Read", :controller =>
''post'', :action =>
''post_read'',
 :user => @user.id :post => @post.id %>

In post_controller:
def post_read
    @postread = UserPost.new(params[:user :post])
    if @postread.save
    flash[:notice] = "Read"
end

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//migration file:
    create_table :posts_users do |t|
      t.column :user_id, :integer
      t.column :post_id, :integer
    end
  
Join tables, by default, are expected to have the tables they join in 
alpha order, hence posts_users rather than users_posts.

comfort eagle wrote:
> I have three tables.  users, posts, users_posts.  This last one is to 
> mark a post as read.
>
> How do I write to the users_post table?
>
> Here''s what I have:
>
> In model ''User_Post''
> belongs_to :post
> belongs_to :user
>
> In post/view/show:
> <%= link_to "Mark As Read", :controller =>
''post'', :action =>
> ''post_read'',
>  :user => @user.id :post => @post.id %>
>
> In post_controller:
> def post_read
>     @postread = UserPost.new(params[:user :post])
>     if @postread.save
>     flash[:notice] = "Read"
> end
>
>

David Chelimsky wrote:
> //migration file:
>     create_table :posts_users do |t|
>       t.column :user_id, :integer
>       t.column :post_id, :integer
>     end
> 
> Join tables, by default, are expected to have the tables they join in
> alpha order, hence posts_users rather than users_posts.
Thanks, then what?

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comfort eagle wrote:
> David Chelimsky wrote:
>   
>> //migration file:
>> ...
>> Join tables ...
> Thanks, then what?
I thought you asked how to write the table, but now I see you asked how 
to write TO the table. Sorry for answering the wrong question :)

DHH talked about this in his keynote at RailsConf - the idea is that you 
should think of PostUser (Posting?) as a first class citizen of your 
domain, and give it its own model and controller. In your case you may 
not need the controller, but if you give it a model you can do this in 
your PostsController (validation excluded for brevity):

  def create
    @post = Post.new(params[:post])
    @post.save
    Posting.new(:user_id => params[:user_id], :post_id => @post.id).save
  end

Cheers,
David

David Chelimsky wrote:
> comfort eagle wrote:
>> David Chelimsky wrote:
>>   
>>> //migration file:
>>> ...
>>> Join tables ...
>> Thanks, then what?
> I thought you asked how to write the table, but now I see you asked how
> to write TO the table. Sorry for answering the wrong question :)
> 
> DHH talked about this in his keynote at RailsConf - the idea is that you
> should think of PostUser (Posting?) as a first class citizen of your
> domain, and give it its own model and controller. In your case you may
> not need the controller, but if you give it a model you can do this in
> your PostsController (validation excluded for brevity):
> 
>   def create
>     @post = Post.new(params[:post])
>     @post.save
>     Posting.new(:user_id => params[:user_id], :post_id =>
@post.id).save
>   end
> 
> Cheers,
> David
Instead of "Posting" I have a model for table posts_users
"PostUser".

So substituting this: "PostUser.new(:user_id => params[:user_id], 
:post_id => @post.id).save" results in error:

"blog_development.post_users'' doesn''t exist".

Notice the singular "post" and multiple "users" now for the
table name
in the error msg.

Ideas?

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comfort eagle wrote:
> Instead of "Posting" I have a model for table posts_users
"PostUser".
> 
> So substituting this: "PostUser.new(:user_id => params[:user_id], 
> :post_id => @post.id).save" results in error:
> 
> "blog_development.post_users'' doesn''t exist".
> 
> Notice the singular "post" and multiple "users" now for
the table name
> in the error msg.
> 
> Ideas?
Yup, rename to postings and Posting :-)

The posts_users name is only relevant if you want the automagic of 
has_and_belongs_to_many.  If you don''t, and you have a first class join
model to link posts and users, I''d give it a better name.

Alan

-- 
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>> Instead of "Posting" I have a model for table posts_users
"PostUser".
>> 
>> So substituting this: "PostUser.new(:user_id =>
params[:user_id],
>> :post_id => @post.id).save" results in error:
>> 
>> "blog_development.post_users'' doesn''t
exist".
>> 
>> Notice the singular "post" and multiple "users" now
for the table name
>> in the error msg.
rename to postings and Posting :-)
> 
> The posts_users name is only relevant if you want the automagic of 
> has_and_belongs_to_many.  If you don''t, and you have a first class
join
> model to link posts and users, I''d give it a better name.
I do want the magic though.

-- 
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You won''t get "the magic" because it''s not that kind
of a join. If all you
wanted was to map a user to a post, you could use "the magic" of
has_and_belongs_to_many.  Since you want to store additional information on
that linking table, you need to make that linking table a new model. Then
you use has_many :through to make it work the way you want.

Here''s kinda what you want.

class Readings< ActiveRecord::Base
  belongs_to :post
  belongs_to :user
end
class Post< ActiveRecord::Base
  has_many :readings, :dependent => :destroy
  has_many :users, :through => :readgins
end
class User< ActiveRecord::Base
  has_many :readings, :dependent => :destroy
  has_many :posts, :through => :readings
end

See this for some insight:

http://blog.hasmanythrough.com/articles/2006/04/20/many-to-many-dance-off





On 7/5/06, comfort eagle <steve@fooworks.com>
wrote:
>
> >> Instead of "Posting" I have a model for table
posts_users "PostUser".
> >>
> >> So substituting this: "PostUser.new(:user_id =>
params[:user_id],
> >> :post_id => @post.id).save" results in error:
> >>
> >> "blog_development.post_users'' doesn''t
exist".
> >>
> >> Notice the singular "post" and multiple
"users" now for the table name
> >> in the error msg.
>
> rename to postings and Posting :-)
> >
> > The posts_users name is only relevant if you want the automagic of
> > has_and_belongs_to_many.  If you don''t, and you have a first
class join
> > model to link posts and users, I''d give it a better name.
>
> I do want the magic though.
>
> --
> Posted via http://www.ruby-forum.com/.
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> Rails mailing list
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>
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"@postread = PostUser.new(:user_id => params[:user_id], :post_id => 
params[:post_id]).save" ended up working in my action.


Maybe I''ll have more trouble getting that info out in a meaningful 
manner though.

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