somewhere in the comments, there is a guy calling a function via stringbyevaluatingjavascript string, then having the js in the page call a url scheme myscheme://{… json data …} to return the data.

I initially had the same problem, but I discovered that this works :

NSString *js =@{(function(){\
var obj = doComplicatedThing();
return JSON.encode(obj);
})();};
NSString * output = [webView stringByEvaluatingJavascriptString:js];

and output DOES contain the json return value!!

the trick here is that you need to wrap the js function in a closure
“(function(){return something})();”

I’ve made progress on my project, but I’m running into the non-blocking
aspect of the JS I’m calling. Any tips on doing polling within ObjC, so I can
ask the uiwebview when its done, since apple doesnt offer the two way
bridge in cocoa touch? The webViewDidFinishLoad delegate method doesnt
do me any good here, as the JS isnt finished yet when this method runs.
My cocoa-fu is still rather weak, so its probably a novice question.