no respond_to block in edit action (generated with scaffold)?

Question

Does anyone know why there is no respond_to block for generated edit actions? Every other action in typical scaffold controllers has a respond_to block in order to output html and xml formats. Why is the edit action an exception?

I'm using the latest version of Ruby on Rails (2.1.1).

Answer 1

Rails handles the 99% case: It's fairly unlikely you'd ever need to do any XML or JSON translations in your Edit action, because non-visually, the Edit action is pretty much just like the Show action. Nonvisual clients that want to update a model in your application can call the controller this way

GET /my_models/[:id].xml (Show) 

Then, the client app can make any transformations or edits and post (or put) the results to

PUT /my_models/[:id].xml (Update) 

When you call this, you usually are doing it to get an editable form of the Show action:

GET /my_models/[:id]/edit 

And it is intended for human use. 99% of the time, that is. Since it's unusual to transform the data in the Edit action, Rails assumes you aren't going to, and DRYs up your code by leaving respond_to out of the scaffold.

Answer 2

Somewhat related. Some may wonder why the rails scaffolding for the new action still has a respond_to block; whereas the edit action does not. This is because a request to something like:

GET /my_models/new.xml

...gives back an XML template that can be used to create a new model.

Answer 3

Because the edit action will only be called from HTML There is no need for the edit form to be returned in an XML context. Using REST, you simply make a put call directly to update with the relevant information.