子線程裏調用performSelector須要注意什麼

如下代碼執行順序是什麼 ?

- (void)action {     NSLog(@"1");     dispatch_queue_t queue = dispatch_get_global_queue(0, 0);     dispatch_async(queue, ^{         NSLog(@"3");         [self performSelector:@selector(test) withObject:nil afterDelay:0.0f];         NSLog(@"4");     });     NSLog(@"2"); }   - (void)test {     NSLog(@"5"); }

 

結果

2019-07-02 09:24:18.492671+0800 ModelTest[12945:510979] 1 2019-07-02 09:24:18.492776+0800 ModelTest[12945:510979] 2 2019-07-02 09:24:18.492807+0800 ModelTest[12945:511386] 3 2019-07-02 09:24:18.493009+0800 ModelTest[12945:511386] 4

 

test方法沒有調用。由於子線程裏runloop默認是關閉的。改成一下代碼後

- (void)action {     NSLog(@"1");     dispatch_queue_t queue = dispatch_get_global_queue(0, 0);     dispatch_async(queue, ^{         NSLog(@"3");         [self performSelector:@selector(test) withObject:nil afterDelay:0.0f];         [[NSRunLoop currentRunLoop]run];         NSLog(@"4");     });     NSLog(@"2"); }   - (void)test {     NSLog(@"5"); }

結果

2019-07-02 09:38:40.874213+0800 ModelTest[13094:524707] 1 2019-07-02 09:38:40.874530+0800 ModelTest[13094:524707] 2 2019-07-02 09:38:40.874551+0800 ModelTest[13094:524802] 3 2019-07-02 09:38:43.792863+0800 ModelTest[13094:524802] 5 2019-07-02 09:38:43.793109+0800 ModelTest[13094:524802] 4