1.GCD
特點：易用，易讀，直觀，靈活，高性能
gcd其實沒有線程的概念，其實gcd的多線程是由于多任務(wù)概念帶來的效果
//創(chuàng)建子線程執(zhí)行dispatch_async(dispatch_get_global_queue(0, 0), ^{ //... });//在主線程執(zhí)行dispatch_async(dispatch_get_main_queue(), ^{ //... });

2.NSThead

特點：基礎(chǔ)，易維護

NSThread* myThread = [[NSThread alloc] initWithTarget:self selector:@selector(threadInMainMethod:) object:nil];
[myThread start];

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

3.NSOperation

特點：系能高，安全可靠，功能強大，控制性強，線程池實現(xiàn)

NSOperationQueue *queue = [[NSOperationQueue alloc] init];

NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^(){
NSLog(@"執(zhí)行第1次操作，線程：%@", [NSThread currentThread]);
}];

NSBlockOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^(){
NSLog(@"執(zhí)行第2次操作，線程：%@", [NSThread currentThread]);
}];
// operation1依賴于operation2
[operation1 addDependency:operation2];

[queue addOperation:operation1];
[queue addOperation:operation2];

4.performSelectorInBackground

特點：易用，清潔，同NSThead

[self performSelectorInBackground:@selector(run) withObject:nil];