multi_page_form_in_rails.txt

Creating a Multi Page Form in Rails

Creating a multi-step wizard-like form is pretty difficult in Rails. 
Especially when trying to apply REST and validations. There are many 
different approaches to this problem, and the right one depends largely 
on your application details. Here are four options, and then my final 
recommendation. Skip to that if you're in a hurry.

1. Create the model at the beginning on the first page of the form, and 
have each successive page update the model. Validations are tricky 
here, but you can use acts_as_state_machine to keep track of the 
different states, and add some conditions to validations to trigger 
them at different states. One downside is that if they stop halfway 
through you end up with a model which is only partially complete. But 
then again, this may be an advantage because it saves their progress 
and they can go back and finish it.

2. Have each form pass the previous form values with hidden fields, and 
then create the model at the very end. Validation is tricky here as 
well. You can either handle it like the first approach, or do it all at 
the very end and figure out how to redisplay the invalid fields.

3. Use Javascript to make one long form look like a multi-step form. 
This way, as far as Rails is concerned, it is just like any other form 
which simplifies a lot. Then, if there's a validation error at the end, 
just return all of the fields again like normal, and hide the ones that 
are valid with Javascript/CSS.

4. Split the one large model up into multiple models, one for each step 
in the form. This way you're just creating a model at each step and the 
validations are handled separately on each one. Usually with this you 
have one primary model and multiple other models associated to that 
with has_one or has_many.

Option 4 is close to my final recommendation, but not quite. I 
recommend not using a multi-page forms. They are difficult to 
implement, and they often result in a poor user experience. The user 
has questions like "what if I have to stop or my browser crashes? do I 
have to enter this all over again?". It's also easy to request more 
information from the user then you actually need.

Instead, ask yourself, what is the minimal amount of information 
required from the user to get started. Have that be a single page form 
which creates the primary model and then lead to the "show" page for 
that model. This can contain an overview of the info they submitted 
along with default values for the rest of the details. This page can 
have links for editing these other details, which will take them to 
other forms for creating the other associated models.

This way you turn a multi-step form into an interactive application. 
Not only does this lead to a better user experience, but is usually 
easier to implement and simplifies the models. This is the REST 
approach.

Ryan Bates
http://railscasts.com