- 最常用GCD方法
dispatch_async(dispatch_get_global_queue(0,0),^{
NSLog(@"Start task 1");
[NSThread sleepForTimeInterval:3];
dispatch_async(dispatch_get_main_queue(),^{
//回到主线程刷新UI
NSLog(@"刷新UI");
});
});
- 系统分配子线程应用
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSLog(@"start task 1");
[NSThread sleepForTimeInterval:2];
NSLog(@"end task 1");
});
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
NSLog(@"start task 2");
[NSThread sleepForTimeInterval:2];
NSLog(@"end task 2");
});
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
NSLog(@"start task 3");
[NSThread sleepForTimeInterval:2];
NSLog(@"end task 3");
});
- 自行创建子线程
//NULL == DISPATCH_QUEUE_SERIAL （同步线程）
// DISPATCH_QUEUE_CONCURRENT (异步线程)
dispatch_queue_t queue = dispatch_queue_create("com.test.gcg.queue", DISPATCH_QUEUE_CONCURRENT);
dispatch_async(queue, ^{
NSLog(@"start task 1");
[NSThread sleepForTimeInterval:2];
NSLog(@"end task 1");
});
dispatch_async(queue, ^{
NSLog(@"start task 2");
[NSThread sleepForTimeInterval:2];
NSLog(@"end task 2");
});
dispatch_async(queue, ^{
NSLog(@"start task 3");
[NSThread sleepForTimeInterval:2];
NSLog(@"end task 3");
});
- 线程组
dispatch_queue_t queue1 = dispatch_queue_create("com.test.gcg.group", DISPATCH_QUEUE_CONCURRENT);
dispatch_group_t group = dispatch_group_create();
dispatch_group_async(group, queue1, ^{
NSLog(@"start task 1");
[NSThread sleepForTimeInterval:2];
NSLog(@"end task 1");
});
dispatch_group_async(group, queue1, ^{
NSLog(@"start task 2");
[NSThread sleepForTimeInterval:2];
NSLog(@"end task 2");
});
dispatch_group_async(group, queue1, ^{
NSLog(@"start task 3");
[NSThread sleepForTimeInterval:2];
NSLog(@"end task 3");
});
- 线程组高级应用，很常见的情形：开辟两个网络请求，都结束之后，执行下一步操作。
（1）比较常规的做法是设置标示符，两线程结束后分别修改状态，两个标识符都改变后，执行下一步操作。
（2）运行线程组的：
dispatch_group_notify；
dispatch_group_enter(group);
dispatch_group_leave(group);
组合能完美解决此问题：
dispatch_group_enter(group);
[self sendRequest1:^{
NSLog(@"request1 done");
dispatch_group_leave(group);
}];
dispatch_group_enter(group);
[self sendRequest1:^{
NSLog(@"request2 done");
dispatch_group_leave(group);
}];
dispatch_group_notify(group, queue1, ^{
NSLog(@"All tasks over");
dispatch_async(dispatch_get_main_queue(), ^{
NSLog(@"回到主线程刷新UI");
});
});
-(void)sendRequest1:(void(^)())block{
dispatch_async(dispatch_get_global_queue(0,0),^{
NSLog(@"start task 1");
[NSThreadsleepForTimeInterval:2];
NSLog(@"end task 1");
dispatch_async(dispatch_get_main_queue(),^{
if(block){
block();
}
});
});
}
-(void)sendRequest2:(void(^)())block{
dispatch_async(dispatch_get_global_queue(0,0),^{
NSLog(@"start task 2");
[NSThreadsleepForTimeInterval:2];
NSLog(@"end task 2");
dispatch_async(dispatch_get_main_queue(),^{
if(block){
block();
}
});
});
}