ruby on rails - Difference between form_for and form_tag?

Question

I used this gem in my application, but I'm not sure the difference between the different implementation options for the gem:

• form_for
• form_tag with block
• form_tag without block

Can anyone clarify? I understand that form_for is used when you wish to interact with a model, but what about the other two?

Answer 1

The differences are subtle, but important. form_for is a more advanced tool that yields an object you use to generate your form elements:

<% form_for(@foo) do |form| %>
  <%= form.text_field(:bar) %>
<% end %>

The form_tag method is much more primitive and just emits a tag. If you want to put things inside of the <form> tag that's emitted, you put things inside the block:

<% form_tag do %>
  <%= text_field_tag(:bar, 'bar_value') %>
<% end %>

Note that the form_for method handles grabbing values from your model, and will at least try to route the form to the appropriate action. With form_tag you are responsible for everything as it makes no assumptions about what you're doing.