Question

i.e., I am creating a new thread like this:

[NSThread detachNewThreadSelector:@selector(doSomething) toTarget:self withObject:nil];

will this automatically make my app multithreaded or must I do some extra work somewhere?

Answer 1

It’s automatic. In the docs for that method:

If this thread is the first thread
detached in the application, this
method posts the
NSWillBecomeMultiThreadedNotification
with object nil to the default
notification center.

GUI Cocoa apps are pretty much always multithreaded these days.