Question

Is there a way to find the thread id that is associated with ‘dispatch_get_main_queue()’?

Answer 1

Any block evaluated on the main queue will evaluate on the thread it is associated with, so you can get the ID of that thread by asking what thread such a block is evaluating on:

#import <mach/mach_init.h>

__block mach_port_t mainThreadID;
dispatch_async(dispatch_get_main_queue(), ^{
    mainThreadID = mach_thread_self();
});

(A mach_port_t is really just an unsigned int.)