Ruby on Rails: Are “form_for(:product, …)” and “form_for(@product, …)” equivalent?

Question

Is

<%= form_for(:product, :url => {:action => \'update\', :id => @product.id})) do |f| %>
  ...
<% end %>

and

<         


        

Answer 1

The @product in the form_for helper ships with more features.

The :product only affects the input field's id and name. For example you have a text filed in the form:

<%= form_for :product, :url => {...}　do |f| %>
  <%= f.text_field :price %>
<% end %>

The generated html would look like:

The id and name value is determined by the :product.to_s and the text field name.

While if you use @product, the :url is not necessary because the url would be determined according to the @product's status:

• if the @product is a new record, the url would post to create
• otherwise, the url would post to update

And the input filed's id and name is affected by @product's class name, so it's important when you're using single table inheritant. The input filed's value is automatically assigned with the @product's attribute value. So if you use @product, the html output would look like:

Assume the @product's class name is Item, then the output would change to:

And of course you can use both of :product and @product:

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

The :product controls input filed's name and id, and the @product controls the url and input field's value.