Rails - Jan 2007 - Preferred find method: :has_many, :belongs_to relationship

I''m looking for some clarification regarding finds in a :has_many,
:belongs_to relationship. Consider:

class User < ARB
  has_many :tasks
end

class Task < ARB
  belongs_to :user
end

Both of these methods in a controller yield the same result:

def find_tasks_for_user
  @user = User.find(params[:id])
  @tasks = Task.find_all_by_user_id(params[:id])
end

def find_tasks_for_user
  @user = User.find(params[:id])
  @tasks = @user.tasks
end

I''m assuming that the latter is the more idiomatic of the two. But is
there anything "wrong" with the first approach?


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On 1/25/07, gmacgregor
<gmacgregor-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
> I''m looking for some clarification regarding finds in a :has_many,
> :belongs_to relationship. Consider:
>
> class User < ARB
>   has_many :tasks
> end
>
> class Task < ARB
>   belongs_to :user
> end
>
> Both of these methods in a controller yield the same result:
>
> def find_tasks_for_user
>   @user = User.find(params[:id])
>   @tasks = Task.find_all_by_user_id(params[:id])
> end
>
> def find_tasks_for_user
>   @user = User.find(params[:id])
>   @tasks = @user.tasks
> end
>
> I''m assuming that the latter is the more idiomatic of the two. But
is
> there anything "wrong" with the first approach?
>
No, but the second approach lends itself to being optimized using
:include - thusly:

def find_tasks_for_user
  @user = User.find(params[:id], :include => :task)
  @tasks = @user.tasks
end

Or the :include can be added to the model definition.

There may also be some advantages in that @user.tasks will cache the value, so
that if code in the view asks for it again, it will avoid another trip
to the DB.

-- 
Matt Jones
mdj.acme-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
President/Technical Director, Acme Art Company (acmeartco.org)

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