How can I get the main thread to sleep while waiting for a delgate to be called?
- by Erik B
Consider a class with these methods:
- (id) initWithFrame: (CGRect) frame
{
if (!(self = [super init]))
return nil;
webView = [[UIWebView alloc] initWithFrame:frame];
[webView setDelegate:self];
lock = [[NSConditionLock alloc] initWithCondition:LOCK_WAIT];
return self;
}
- (void) setHTML: (NSString *) html
{
[lock lockWhenCondition:LOCK_WAIT];
[webView loadHTMLString:html baseURL:nil];
[lock unlock];
}
- (void)webViewDidFinishLoad:(UIWebView *)aWebView
{
[lock lockWhenCondition:LOCK_WAIT];
// Locking to be able to unlock and change the condition.
[lock unlockWithCondition:LOCK_GO];
}
- (NSString *) stringByEvaluatingJavaScriptFromString: (NSString *) jsCommand
{
[lock lockWhenCondition:LOCK_GO];
return [webView stringByEvaluatingJavaScriptFromString:jsCommand];
[lock unlock];
}
Let's call this class SynchronousUIWebView.
From the main thread I execute:
webView = [[SynchronousUIWebView alloc] initWithFrame:frame];
[webView setHTML:html];
[webView stringByEvaluatingJavaScriptFromString:jsCommand];
The problem seems to be that the delegate is not called until I leave the current call stack, which I don't since I'm waiting for the delegate call to happen, aka deadlock. To me it seems like the delegate call is pushed to a queue that is called when the current call is done. So the question is can I modify this behavior?
Note: The reason this is needed is that I can't execute the JavaScript until the HTML has loaded.
