Question

I am trying to get data for my collection_select list.

Details

There are 4 tables involved

       volunteers 
            has_many :signed_posts
            has_many :posts, :through=>:signed_posts

       signed_posts
            belongs_to :volunteer
            belongs_to :post

       posts
            belongs_to :organization
            has_many :signed_posts
            has_many :volunteers, :through=>:signed_posts

       organizations
            has_many :post

If I would have to write in plain SQL, it would be like below.This sql is for postgreSQL. I would like to write in rails 3.2.1 syntax.

      Select sp.id,p.title ||'-'|| o.name AS project from signed_posts sp 
           inner join volunteers v on v.id=sp.volunteer_id
           inner join posts p on p.id=sp.post_id
           inner join organizations o on o.id=p.organization_id
           where v.id=1

As a result, I want to get signed_posts.id and posts.title – organizations.name for a volunteer id 1

which I would like to use on dropdown list.

Thank you very much for your help

My Solution

I solved the problem using hash table like this one

        @signed_projects=Volunteer.find(1).signed_posts.joins(:post)

        @ddl_test=Hash.new
            @signed_projects.each do |signed_project|
                   ddl_test[signed_project.post.title+"-"+signed_project.post.organization.name]=signed_project.id

           end

On View

                <%=select_tag 'ddl_test',options_for_select(@ddl_test.to_a),:prompt => 'Please select the project'%>

I am not completely satisfied. I think there must be some elegant solution. If any body has better idea, please let me know

Answer 1

There are a couple ways to do this. In your controller you would want a statement such as:

@signed_posts = Volunteer.find(1).signed_posts.includes({:post => :organization})

After that, one way would be to create a method in your SignedPost model to return the data you need, something like the following

def post_name_with_organization
  "#{id} #{post.title} - #{post.organization.name}"
end

Then, in your collection_select, you can use (this is partially guessing, since I don’t know the specifics of your form):

form.collection_select(:signed_post_id, @signed_posts, :id, :post_name_with_organization)

Edit based on question updates

If you want to use select_tag and options_for_select as you did in your solution, a more elegant way would be to create this variable in your controller:

@signed_posts_options = @signed_posts.map {|sp| [sp.post_name_with_organization, sp.id]}

Then in your view:

<%=select_tag 'ddl_test',options_for_select(@signed_posts_options),:prompt => 'Please select the project'%>