Question

I have an issue that looks like a race condition with a webview callback and a location manager callback that interact with the same variables and an alert dialog – the dialog is created in the location callback and should be dismissed in the webview callback. I thought that the delegate callbacks for standard objects like the webview and core location would be run in the main thread – is that not correct?

Answer 1

If in doubt then you can do something like this:

- (void) someCallback
{
    if ([NSThread isMainThread] ==  NO) {
        [self performSelectorOnMainThread: @selector(someCallback)];
    }
}

To make sure that you are always executing callback methods on the main thread and thus preventing concurrency issues.

You can also use a @synchronized block of course, but in my experience it is much better to rely on the synchronous nature of executing methods on the main thread.