JSONP Support

[mdespuits]

As this has some bearing with Javascript web applications, any plans on adding support for JSONP output?

[bigjason]

JSONP is not really a format, it is more of a javascript technique really. The hard part being that on the server, you specify a callback for the client. Where would that callback be coming from? Would it be different in each request?

I am not trying to rain on any parades. I actually have a need for this as well, but can't quite picture the implementation. Do you have anything in mind?

[mdespuits]

Not in particular. The only thing I noticed is that there was not a very simple way to wrap the JSON output jBuilder makes with a function callback. That's really what I was thinking about was the just the function wrapper. If this is not planned or is better fit somewhere else, I completely understand, but I really like using this gem and figured I would ask if that was a possibility.

[bigjason]

It may be. I am not actually affiliated with @dhh or anything. My company just uses this gem heavily and so we contribute when we can.

If you are using rails 3.1+ I think that you could actually write a sprockets processor to do this for you. Something that takes the output of the previous step and wraps it in a function. Something like:

class JSONPTemplate < Tilt::Template
  def self.default_mime_type
    'application/javascript'
  end
  def prepare
  end

  def evaluate(scope, locals, &block)
    "somethingClientSide(#{data});"
  end
end

Sprockets.register_engine '.jsonp', JSONPTemplate

Then you name your templates something like accounts.jsonp.jbuilder and it will create the jsonp output exactly how you want it.

[bigjason]

Uhhh. Don't try to use the above. That is for assets not for templates.

[bigjason]

Ok I have made a solution. It is an alternate template extension that will look for a callback param and format to JSONP if it finds it. You can get it here: https://rubygems.org/gems/jpbuilder. I think that it may work as an inclusion in Jbuilder so I may create a pull request for it later.

[mdespuits]

Wow, that's fantastic! Thanks @bigjason.