Delegate all method calls on a model to an association

Question

I am having an ActiveRecord model with a polymorphic association like this:

class Reach < ActiveRecord::Base   belongs_to :reachable, :polymorphic => true end 

This model acts like a proxy. What I need to do is to forward all method calls on that object to the associated object :reachable. I think delegate won't help here because I have to explicitly name all the methods I need to delegate. I need something like delegate :all to delegate all methods (not all method).

Answer 1

Since Rails 5.1+ you can delegate everything not implemented with delegate_missing_to :reachable

Basically, do what you expect. You could read more on the Api Doc

If you are stuck in a previous version then just recommend using the method_missing from @Veraticus answer, is less performance-wise as mentioned but I think is the more flexible approach.

Answer 2

There are two things you can do here:

1. The slower (performance-wise) but easier method is to use method_missing:

   class Reach < ActiveRecord::Base    def method_missing(method, *args)     return reachable.send(method, *args) if reachable.respond_to?(method)     super   end end 

2. The faster performing method would be to define each method dynamically that you want to delegate:

   class Reach < ActiveRecord::Base    [:all, :my, :methods, :here].each do |m|     define_method(m) do |*args|       reachable.send(m, *args)     end    end end 

You could even use that method in a more dynamic manner, if you wanted, by taking the Reach class, finding the methods that are defined on it and it alone, and defining only those on Reachable. I would do it by hand though because there are some you probably won't want to include.