Implementing tags in Rails: how to reference multiple elements with a single tag?

Question

I am writing a blog engine in rails, and have set up a tag model and a post model that has has_and_belongs_to_many relationships. Adding a tag works fine, the problem occurs when searching for all posts with a specific tag:

If I add the “test” tag to Post A, add the “test” tag to publish B, there are two tag objects, both with the name “test”, but with different identifiers, both refer to different messages. Now, if I have an actionTagPosts controller that accepts the "tag" parameter and finds all messages with this tag, it will return only one message, since the other tag has a different identifier and is not actually connected. Should I somehow limit the addition of new tags, or should I manipulate how I pull all the relevant tags differently?

Here is a controller action that should capture all relevant messages based on the 'tag' parameter:

def indexTagPosts

        @tag = Tag.find(params[:tag])
        @posts = @tag.posts.all

end

And here is the action to save the tag:

def create


    @post = Post.find(params[:post_id])
    @tag = @post.tags.create(params[:tag])

    respond_to do |format|
      if @tag.save
        format.html { redirect_to edit_post_path(@post),:notice => "Success" }
      end
    end  

end

Thanks in advance and apologies for the redundancy or poor wording.

Answer 1

, has_and_belongs_to_many, , . , has_many ..., :through, .

, , , , :

class Post < ActiveRecord::Base
  has_many :post_tags
  has_many :tags, :through => :post_tags
end

class Tag < ActiveRecord::Base
  has_many :post_tags
  has_many :posts, :through => :post_tags
end

class PostTag < ActiveRecord::Base
  belongs_to :post
  belongs_to :tag
end

:

@post = Post.find(params[:post_id])

if (params[:tags].present?)
  @post.tags = Tag.where(:name => params[:tags].split(/\s*,\s*/))
else
  @post.tags = [ ]
end

has_many , PostTag .

, Post, , :

 class Post
   def tags_used
     self.tags.collect(&:name).join(',')
   end

   def tags_used=(list)
     self.tags = list.present? ? Tag.where(:name => list.split(/\s*,\s*/)) : [ ]
   end
 end