Question

I’m writing a multi threaded application for iOS.
I am new to Objective-C, so I haven’t played around with threads in iPhone before.

Normally when using Java, I create a thread, and send “self” as object to thread. And from the thread I can therefor call the main thread.
How is this done in Objective C?

How can I call the main thread from a thread? I have been trying with NSNotificationCenter, but I get a sigbart error :/

This is how the thread is started:

NSArray *extraParams = [NSArray arrayWithObjects:savedUserName, serverInfo, nil];       // Parameters to pass to thread object

NSThread *myThread = [[NSThread alloc] initWithTarget:statusGetter                      // New thread with statusGetter
                                             selector:@selector(getStatusFromServer:)   // run method in statusGetter
                                               object:extraParams];                     // parameters passed as arraylist
[myThread start];                                                                       // Thread started

activityContainerView.hidden = NO;
[activityIndicator startAnimating];

Any help would be great!

Answer 1

you accomplish this by adding a message to the main thread’s run loop.

Foundation provides some conveniences for this, notably -[NSObject performSelectorOnMainThread:withObject:waitUntilDone:] and NSInvocation.

using the former, you can simply write something like:

[self performSelectorOnMainThread:@selector(updateUI) withObject:nil waitUntilDone:NO]

a notification may be dispatched from a secondary thread (often the calling thread).