Belongs_to :through

Rails
1

Why is belongs_to :through not an option with Rails? I’m sure there
is something I’m missing! I find myself wanting it more now with lazy
loading in Rails 3.

project belongs_to client

task belongs_to project
task belongs_to client :through project

I can work around it by just creating a method on the task model
called client and just returns project.client, but that isn’t as
beautiful!

Thanks,
Tom

2

On Sat, Nov 6, 2010 at 1:13 AM, TomRossi7 [email protected] wrote:

called client and just returns project.client, but that isn’t as
beautiful!

Thanks,
Tom

What you’re really looking for is has_one :through.

–
Erol M. Fornoles

http://twitter.com/erolfornoles
http://ph.linkedin.com/in/erolfornoles

3

I’m not sure how the has_one relationship is translating for scopes,
but here is an example that causes problems:

Task.joins(:client).where(‘clients.name’ => ‘test’)

results in the following SQL:

SELECT tasks.* FROM tasks INNER JOIN projects ON tasks.id IS
NULL INNER JOIN clients ON clients.id = projects.client_id
WHERE (clients.name = ‘test’)

I realize I can do Task.joins(:project => :client), but that is what I
am trying to avoid for my complicated scopes.

Thanks,
Tom

4

belongs_to :through definitely is not necessary just like
has_many :through is not necessary and wasn’t even included in earlier
releases of Rails. With Rails 3, creating scopes that are lazily
loaded provides a lot of functionality that would be nice to extend to
the belongs_to :through relationship.

5

On Nov 5, 1:13pm, TomRossi7 [email protected] wrote:

Why is belongs_to :through not an option with Rails? I’m sure there
is something I’m missing! I find myself wanting it more now with lazy
loading in Rails 3.

project belongs_to client

task belongs_to project
task belongs_to client :through project

belongs_to :through is not necessary, which is why it’s not an option.

So you are saying your tables would look like this:

TASK
name
project_id

PROJECT
name
client_id

CLIENT
name

And you would like to be able to find all tasks for a given client?

In that case, you would say client has_many :tasks, :through
=> :project

Then instead of “Task.joins(:project => :client)” You can do
“Client.find_by_name(‘asdf’).tasks”