I understand what is passed to the form_for method when doing something like :
<% form_for(@user) do |f| %> ... <% end %>
if @user is set in the controller. This is pretty obvious.
But what happens when we pass :user, as I have seen in many examples ?
<% form_for(:user) do |f| %> ... <% end %>
When should I use the symbol version ?
Using the symbol will generate:
<form action="/users" method="post">
Using the object @user set to new you get:
<form action="/users/create" class="new_user" id="new_user" method="post">
If you set @user to something else it will change the form tag generated, of course ... try it out for yourself.
In the end it all depends what you're trying to do. You might want to use the symbol if you have multiple :user forms on the same page.