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?
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.
One uses model binding and the other doesn't
As far as I know there is only one simple difference. form_tag without a block will only generate a html element for you. When you use form with a a block it will also create the form closing tag .
In example:
<% form_tag("/comments") %>
will result in
<form action="/comments">
Where
<%= form_tag("/comments") do %>
<%= submit_tag %>
<% end %>
will generate
<form action="/comments">
<input type="sumbit" />
</form>
来源：https://stackoverflow.com/questions/9540291/difference-between-form-for-and-form-tag