Question

How can I do a cross-model find in a way which conforms most closely to the MVC pattern?

I have a model, Istc.rb. In the index view that corresponds to this model, I want to do this:

   = "Last edited by #{User.find_by_id(istc.user_id).first_name}"    

Clearly you can’t have a model.find in a view – and not only is this a model.find, it’s a find on a different model. But how would you refactor this?

I’m nervous about having a helper like this because it’s still pretty close to the View layer:

module UsernameHelper
  def user_name(model)
    User.find_by_id(model.user_id) unless User.find_by_id(model.user_id).nil?
  end
end

Is the way to do it to have a scope on User?

# User.rb
scope :lookup, lambda {|model| where("id = ?", model.user_id)}

# username_helper.rb
module UsernameHelper
  def user_name(model)
    User.lookup(model).first unless User.lookup(model).first.nil?
  end
end

Or should the istcs_controller handle it? Or should there be a separate controller, which talks to both the Istc and User model?

Thoughts welcome, and I’d really like to see any sample applications which solve this sort of problem elegantly, too.

Answer 1

As Rasmus said, if we make use of association its a simple think,
User Model:

class User < ActiveRecord::Base
   has_many :istcs, :class_name => "Istc"
end

Istc Model:

class IStc < ActiveRecord::Base
  belongs_to :user
end

view:

<%= "Last edited by #{istc.user.first_name}" %>

If you are not happy with this the following would be the alternate solutions,

1. Write a helper method in application_herlper.rb(Since you are using in different controller views.
2. Write a instance method in Istc.rb model, that you could call from one the istc object directly from the view.