这是一个需求
假设有3个操作，需要其中一个操作需要在另外两个操作之后执行~
第一种方式
dispatch_group_t group = dispatch_group_create();
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_group_async(group, queue, ^{
//block 1
NSLog(@"block 1 start~");
[NSThread sleepForTimeInterval:1.0];
NSLog(@"block 1 end~");
});
dispatch_group_async(group, queue, ^{
//block 2
NSLog(@"block 2 start~");
[NSThread sleepForTimeInterval:2.0];
NSLog(@"block 2 end~");
});
dispatch_group_notify(group, queue, ^{
//block 3
NSLog(@"block 3~");
self.view.backgroundColor = [UIColor whiteColor];
});
第二种方式
NSOperationQueue *operationQueue = [[NSOperationQueue alloc] init];
NSBlockOperation *blockOperation1 = [NSBlockOperation blockOperationWithBlock:^{
//code~
NSLog(@"block 1 start~");
sleep(2);
NSLog(@"block 1 end~");
}];
NSBlockOperation *blockOperation2 = [NSBlockOperation blockOperationWithBlock:^{
//code~
NSLog(@"block 2 start~");
sleep(1);
NSLog(@"block 2 end~");
}];
NSBlockOperation *blockOperation3 = [NSBlockOperation blockOperationWithBlock:^{
//code~
NSLog(@"block 3");
}];
[blockOperation3 addDependency:blockOperation1];
[blockOperation3 addDependency:blockOperation2];
[operationQueue addOperation:blockOperation1];
[operationQueue addOperation:blockOperation2];
[operationQueue addOperation:blockOperation3];
thoughts
* 如果需要对线程进行细颗粒度的处理，那么还是NSOperation &NSOperationQueue更具有优势~
像优先级，并行操作数，取消操作等~
* 简单操作，GCD的方式更加简洁优雅~