Sometimes we need form without model creation - for example search field or email, where should be send some instructions. What is the best way to create this forms? Can i create virtual model or something like this? I'd like to use formtastic, but not form_tag.
Firstly, Formtastic doesn't need a model in all cases, although it certainly works best and requires less code with a model.
Just like Rails' own built-in form_for, you can pass in a symbol instead of an object as the first argument, and Formtastic will build the form and post the params based on the symbol. Eg:
<% semantic_form_for(:session) do |f| %>
...
<% end %>
This will make the form values available to your controller as params[:session].
Secondly, a model doesn't mean an ActiveRecord model. What I mean is, Formtastic will work with any instance of a class that quacks like an ActiveRecord model.
A classic example of this that many people are using Authlogic for authentication with Formtastic. Part of Authlogic is the idea of a UserSession model, which works fine:
Controller:
def index
@user_session = UserSession.new
end
Form:
<% semantic_form_for(@user_session) do |f| %>
<%= f.input :login %>
<%= f.input :password %>
<% end %>
This will make your form data available in your controller as params[:user_session].
It's really not that hard to create a model instance to wrap up the concerns of your model. Just keep implementing the methods Formtastic is expecting until you get it working!