Is it possible to run some javascript code (having perhaps an NSString as input) without using a UIWebView? I would like to run this code in a separate thread so UIWebView is not possible and I don't really want to render anything, just get back the results.
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3 Answers
I have not tried this, but here is one idea:
Write code to allocate an empty UIWebView but doesn't add it as a subview anywhere, and just directly call - (NSString *)stringByEvaluatingJavaScriptFromString:(NSString *)script on your javascript.
Then use NSOperation to run that in parallel.
Any reason that might not work for you? I think it would avoid displaying anything for the UIWebView.
As a side note, I can't think of anything you can do in javascript that you can't do more quickly directly in Objective-C. Except maybe parsing javascript that you get externally, which may be considered a no-no by Apple, depending on the details.
Guessing at your goals: If you want to parse a JSON server reply, I recommend the json-framework library hosted on google code. It has a nice interface, and it is surprisingly easy to learn and integrate.
3 Comments
user130444
This doesn't seem to work, for every UIWebView method I try to call I get "bool _WebTryThreadLock(bool), 0xf42930: Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread. Crashing now..." As for my reasons, I'm mostly experimenting :)
Vincent Gable
Unless explicitly documented, it's not safe to call ANY method other than retain* on a UIKit object. So I wouldn't expect this to ever work.
Vincent Gable
*technically release is thread-safe by itself, but if you are the last person to release an object, it may cause dealloc to be run on your thread, which is not always safe.
I think Parmanoir's article Taming JavascriptCore within and without WebView may give you some advice.
1 Comment
user130444
JavaScriptCore is not exposed in the SDK (WebKit is a private framework) but the link is very interesting, thanks!
self.timer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(getResults:) userInfo:nil repeats:YES];
-(void)getResults
{
NSString *value = [self.webView stringByEvaluatingJavaScriptFromString:@"javascript"];
}
Any reason you couldn't just do something like this. Shouldn't be that big of an overhead on your main thread.
