I am new to Three20 and have been trying to develop an iPhone app with Three20 for the past week. This app has to access to a xmlrpc server.
I know it is possible to receive responses in other formats like JSON.
But for requests, instead of the provided HTTP class TTURLRequest, is it possible to send request by XML-RPC?
Cocoa XML-RPC Client Framework appears to do what you want, although it uses the underlying NSURLConnection and friends that Three20 uses, not Three20 itself.
For the record, XML-RPC uses HTTP as its transport layer, so I don't see why you wouldn't be able to use it for that purpose in the first place; the main thing is writing a library that wraps the underlying HTTP transport pieces so you can invoke methods more transparently.
(I.e., you can set HTTP headers as well as the request method (GET, POST, PUT, etc.), and submit data in the body of an HTTP request, so everything is there to support it. Additionally, XML itself can be parsed via the NSXMLParser class, the Open Source libxml2 library, or other third-party solutions (e.g. TouchXML, which is built on libxml2).)
Lastly, there is another SO question regarding XML-RPC on the iPhone in general, although it has many of the same answers.
I created three20 extention for XML-RPC connection.
It's on my three20 fork.
http://github.com/ngs/three20/tree/master/src/extThree20XMLRPC/
Please try this and feedback me.