Question

What is the difference between using form_for the following way:

<% form_for @user do |f| %>
   <%= f.label :name %>:
   <%= f.text_field :name, :size => 40 %>
   ...
<% end %>

and:

<% form_for :user, :url => {:action => 'create'} do |f| %>
   <%= f.label :name %>:
   <%= f.text_field :name, :size => 40 %>
   ...
<% end %>

Does using @user just automatically use CRUD methods for the URL actions?

Answer 1

If you give form_for a symbol without an instance variable it looks for an instance variable with the same name.

The documentation says:

For example, if @post is an existing
record you want to edit

<% form_for @post do |f| %>
  ... 
<% end %>

is equivalent to something like:

<% form_for :post, @post, :url => post_path(@post), :html => { :method => :put, :class => "edit_post", :id => "edit_post_45" } do |f| %>
  ...
<% end %>