Which schemes does NSURL / NSURLRequest / NSURLConnection understand?

Question

Apple says, NSURL is developed using RFC 1738 (and some others).

Now RFC 1738 specifies only that an web URL has a scheme and a scheme specific part.

I want to know all the schemes which NSURL understands. And because I use it with NSURLRequest and NSURLConnection (the so called "URL Loader System"), I must know all the schemes which these understand.

Why? Because I just want to know. Apple does not go into detail about it in the documentation, the just say the comply to RFC 1738. That tells a lot and also nothing.

Answer 1

The built-in URL protocols can handle the schemes http, https, file, ftp, about, and data.

You can define your own protocols to make the NSURL system automatically handle new schemes using the NSURLProtocol class.

Answer 2

NSURL "supports" any scheme, because it knows nothing about how to use the scheme in question. It is just a wrapper around the concept of a URL.

Likewise, NSURLRequest knows no more, but it does have capability to store extra information which could be protocol-specific.

NSURLConnection is where you start getting more protocol-specific. NSURLConnection is capable of supporting any URL you throw at it, provided there is a suitable NSURLProtocol subclass registered for that. But out of the box, it is documented to support http:, https:, ftp: and file:. You can test it with a quick +canHandleRequest: call.