Question

I have built a ruby on rails app that lets users track their workouts. User has_many workouts. In addition, a User can create a box (gym) if they are a gym owner. Users can then associate with that box through a Membership resource.

I create that association for the current_user with a remote form in /views/boxes/show.html.erb:

<% remote_form_for Membership.new do |f| %> 
  <%= f.hidden_field :box_id, :value => @box.id %>
  <%= f.hidden_field :user_id, :value => current_user.id %>
  <%= submit_tag "I am a member of this box" , :class => '' %>
<% end %>

I now want to give the current_user the ability to remove their association. How do I structure the link/form and what should the memberships_controller destroy action look like?

Below is a list of my associations if it helps:
User

class User < ActiveRecord::Base
  has_many :boxes
  has_many :workouts, :dependent => :destroy
end

Workout

class Workout < ActiveRecord::Base
  belongs_to :user
  belongs_to :box
end

Box

class Box < ActiveRecord::Base
  belongs_to :user
  has_many :users, :through => :memberships
  has_many :workouts, :through => :users
  has_many :memberships
end

Membership

class Membership < ActiveRecord::Base
  belongs_to :user
  belongs_to :box
end

Answer 1

After you have done the changes suggested here, and assuming that you have obtained the membership for the current_user and the box using the following code,

@membership = current_user.memberships.for_box(box).first

create a link for the user to delete the membership as follows.

link_to 'Delete Membership', membership_path(@membership), :method => :delete

Membership controller should have a destroy method that looks like the following.

def destroy
  @membership = Membership.find(params[:id])
  @membership.destroy
end

This is assuming that your memberships controller is restful and you have map.resources :memberships in your routes.