虚拟属性

Question

<%= form_for(@membership) do |f| %>
  <%= f.collection_select :user_id, User.all, :id, :email %>
  <%= f.collection_select :role_id, Role.all, :id, :name %>
  <%= f.submit %>
<% end %>

What i'm trying to do is instead of using a select box for users, i want to put a text field for users email.

<%= form_for(@membership) do |f| %>
  <%= f.text_field :email %>
  <%= f.collection_select :role_id, Role.all, :id, :name %>
  <%= f.submit %>
<% end %>

Membership.rb

belongs_to :user
belong_to :role

attr_accessor :email
def email
 self.user.email if self.user
end

What i dont know is what to write in controller to make it work and is this attr accessor using thing and email method is ok? Any help is appreciated.

  def create
     @membership = Membership.new(params[:membership])
     if @membership.save
        redirect_to(memberships_url)
      else
       render :action => "new"
  end

Answer 1

I think what you're looking for is a nested form. On the Model that has the has_x designation you can use accepts_nested_attributes_for . There is also a Railscast explaining it. This means you have two decent options:

1. Redefine your form to be for the user and use fields_for to add the Membership attributes
2. Switch your models around so that a User belongs to a Membership and a Membership has_x User(s)

Answer 2

If you want it to update existing users only, you'll have to find the user by email in your create action, since Membership needs a user_id and role_id.