Question

I’m building a recurring billing system and am having trouble with a nested form. The following code works, but makes a POST with:

"customer"=>{"service"=>{"service_id"=>"1"}}

It should be Customer.services instead of Customer.service. However, if I change the form to reference fields_for :services, it doesn’t render a dropdown at all.

_form.html.haml

= form_for @customer do |f|
= f.fields_for :service do |service_fields|
  = service_fields.collection_select(:service_id, Service.all, :id, :name, { :prompt => 'Select Package' })
= f.submit "Add Service", class: "btn"

models/customer.rb

class Customer < ActiveRecord::Base
  has_many :subscriptions, :dependent => :destroy
  has_many :services, :through => :subscriptions

  accepts_nested_attributes_for :services
end

models/service.rb

class Service < ActiveRecord::Base
  has_many :customers, :through => :subscriptions
  has_many :subscriptions
end

models/subscription.rb

class Subscription < ActiveRecord::Base
  belongs_to :customer
  belongs_to :service
end

Answer 1

So, in this situation you want to build a subscription on the customer. Since you’re pretty much on the right track, it should be as simple as changing this

_form.html.haml

= form_for @customer do |f|
= f.fields_for :subscriptions do |subscription_fields|
  = subscription_fields.collection_select(:service_id, Service.all, :id, :name, { :prompt => 'Select Package' })
= f.submit "Add Service", class: "btn"

models/customer.rb

class Customer < ActiveRecord::Base
  has_many :subscriptions, :dependent => :destroy
  has_many :services, :through => :subscriptions

  accepts_nested_attributes_for :subscriptions
end

Right now the reason why you’re getting anything rendered is because you’re causing the form to submit with a new “attribute” called service with then returns the data from the fields_for. With accepts_nested_attributes_for {model} you should be looking for a params with something like {model}_attributes

Also the reason why you’re not getting anything rendered when you use :services in the fields_for is because Service doesn’t respond to service_id.