Question

This has been completed all code below is working.

If your familiar with the R.B Rails Cast that was done on this i am instead trying to work with the “@authorships” form instead of the Book-to-Author itself.

I am using Jquery TokenInput and this is my setup in more detail:

---

Application.js

$(function() {
  $("#user_product_product_token").tokenInput("/products.json", {
    prePopulate: $("#user_product_product_token").data("pre"),
    tokenLimit: 1
  });
});

---

class UserProduct
    attr_accessible :product_token, :price
    belongs_to :user
    belongs_to :product
    attr_reader :product_token

    def product_token=(id)
        self.product_id = id
    end
end

---

class Product
    has_many :user_products
    has_many :users, :through => :user_products
end

---

This gets my /products.json route to work and list all of my products with ID and Name.

class ProductsController

  def index
    @products = Product.where("name like ?", "%#{params[:q]}%")

    respond_to do |format|
      format.json { render :json => @products.map(&:attributes) } # This here
    end
  end

This is my form:

<%= form_for(@user_product) do |f| %>
    <%= f.text_field :product_token, "data-pre" => @products.map(&:attributes).to_json %>
    <%= f.label :price %><br />
    <%= f.text_field :price %>
    <%= f.submit %>
<% end %>

---

class UserProductsController

def new
    @user_product = current_user.user_products.build
    # This just initializes the @products variable for the @products.map and ProductsController.
    @products = []
 end

def edit
    @user_product = UserProduct.find(params[:id])
    # Without this line below it cant find the correct product.
    @products = [@user_product.product]
end

Here’s my gist on it: https://gist.github.com/1116092

Answer 1

Your @products instance variable is not set, as already pointed out by Luke, but but his solution to it is not probably what you want. You want to pre-populate the product if some is already selected in UserProduct. which would not be set as your are creating a new UserProduct in the action, but if you use same form with edit also, then it might be used. I would suggest to modify your action on following lines in both new and edit action:

def new
  @user_product = current_user.user_products.build
  @products = [@user_product.product]

  respond_to do |format|
    format.html # new.html.erb
    format.xml  { render :xml => @user_product }
  end
end

One other thing you need to take care is, set the max option while initializing jquery-token-input to 1, as you can have one user_product belong to only one product.

One other thing I noticed is your method to save product_token, you misssed the actual assignment there:

def product_token=(id)
    self.product_id = id # assign it to product_id
end