collection_select method gives error in Rails 3.1.1

Question

I have a Model called Category and other Model Product. They have has_many and belongs_to relation. But code in my view

    
<%= f.collection_sel         


        

Answer 1

Chances are you have something like this:

<%= form_for @product do |f| %>

Because f is already tied to product, you don't need to include it as your first argument, so it should just be:

<%= f.collection_select :category_id, Category.all, :id, :name %>

Or, you could not use f.:

<%= collection_select :product, :category_id, Category.all, :id, :name %>