看着各位大神10k2k年薪10w的。。

dispatch_group_t group = dispatch_group_create();
dispatch_group_async(group, dispatch_get_global_queue(0,0), ^{
for (int i =0 ; i < 200; i++) {
NSLog(@"第一个线程%d",i);
}
});
dispatch_group_async(group, dispatch_get_global_queue(0,0), ^{
for (int i =0 ; i < 400; i++) {
NSLog(@"第二个线程%d",i);
}
});
dispatch_group_notify(group, dispatch_get_global_queue(0,0), ^{
NSLog(@"汇总线程");
});