#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
//并发队列
dispatch_queue_t q = dispatch_queue_create("myQueue", DISPATCH_QUEUE_CONCURRENT);
//异步任务
dispatch_async(q, ^{
//同步并发
dispatch_sync(q, ^{
NSLog(@"AAAA %@", [NSThread currentThread]);
});
//异步并发
dispatch_async(q, ^{
NSLog(@"BBBB %@", [NSThread currentThread]);
});
//异步并发
dispatch_async(q, ^{
NSLog(@"CCCC %@", [NSThread currentThread]);
});
for (int i = 0; i < 10; i++) {
NSLog(@"%d %@", i, [NSThread currentThread]);
}
});
}
/** 打印结果
2018-10-23 20:27:26.256127+0800 testttt[6530:334192] AAAA <NSThread: 0x600000276840>{number = 3, name = (null)}
2018-10-23 20:27:26.256531+0800 testttt[6530:334192] 0 <NSThread: 0x600000276840>{number = 3, name = (null)}
2018-10-23 20:27:26.256547+0800 testttt[6530:334186] BBBB <NSThread: 0x604000270d00>{number = 4, name = (null)}
2018-10-23 20:27:26.256583+0800 testttt[6530:334184] CCCC <NSThread: 0x604000270dc0>{number = 5, name = (null)}
2018-10-23 20:27:26.256785+0800 testttt[6530:334192] 1 <NSThread: 0x600000276840>{number = 3, name = (null)}
2018-10-23 20:27:26.257096+0800 testttt[6530:334192] 2 <NSThread: 0x600000276840>{number = 3, name = (null)}
2018-10-23 20:27:26.257256+0800 testttt[6530:334192] 3 <NSThread: 0x600000276840>{number = 3, name = (null)}
2018-10-23 20:27:26.257444+0800 testttt[6530:334192] 4 <NSThread: 0x600000276840>{number = 3, name = (null)}
2018-10-23 20:27:26.258598+0800 testttt[6530:334192] 5 <NSThread: 0x600000276840>{number = 3, name = (null)}
2018-10-23 20:27:26.259088+0800 testttt[6530:334192] 6 <NSThread: 0x600000276840>{number = 3, name = (null)}
2018-10-23 20:27:26.260051+0800 testttt[6530:334192] 7 <NSThread: 0x600000276840>{number = 3, name = (null)}
2018-10-23 20:27:26.260641+0800 testttt[6530:334192] 8 <NSThread: 0x600000276840>{number = 3, name = (null)}
2018-10-23 20:27:26.261221+0800 testttt[6530:334192] 9 <NSThread: 0x600000276840>{number = 3, name = (null)}
*/
@end
原因猜想:
-- 异步并发队列 中加入同步任务
-- 同步任务会占用并阻塞当前线程(打印AAAA)
-- 当同步任务执行完毕
-- 当前被阻塞的任务继续(打印0), 且B C 异步执行
纯粹个人猜想，如有问题请看官指导
