for循環(huán)里的異步任務(wù)完成再進(jìn)行其他操作

// 1.創(chuàng)建一個串行隊(duì)列甘晤，保證for循環(huán)依次執(zhí)行
dispatch_queue_t serialQueue = dispatch_queue_create("serialQueue", DISPATCH_QUEUE_SERIAL);
 
// 2.異步執(zhí)行任務(wù)
dispatch_async(serialQueue, ^{
    // 3.創(chuàng)建一個數(shù)目為1的信號量乳绕，用于“卡”for循環(huán)享潜，等上次循環(huán)結(jié)束在執(zhí)行下一次的for循環(huán)
    dispatch_semaphore_t sema = dispatch_semaphore_create(1);
 
    for (int i = 0; i<5; i++) {
        // 開始執(zhí)行for循環(huán)瓦堵，讓信號量-1基协，這樣下次操作須等信號量>=0才會繼續(xù),否則下次操作將永久停止
        dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
        printf("信號量等待中\(zhòng)n");
        // 模擬一個異步任務(wù)
        NSMutableURLRequest *urlRequest = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:@"https://github.com"]];
        NSURLSession *session = [NSURLSession sharedSession];
        NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:urlRequest completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        // 本次for循環(huán)的異步任務(wù)執(zhí)行完畢，這時候要發(fā)一個信號菇用，若不發(fā)澜驮，下次操作將永遠(yuǎn)不會觸發(fā)
            [tampArray addObject:@(i)];
            NSLog(@"本次耗時操作完成，信號量+1 %@\n",[NSThread currentThread]);
            dispatch_semaphore_signal(sema);
 
        }];
        [dataTask resume];
 
        NSLog(@"上傳動態(tài)照片到阿里云成功：%@", fileInfo.filePath);
        NSString *imgUrl = fileInfo.object;
        [self.imageUrls addObject:imgUrl];
        if (self.imageUrls.count == self.imagePaths.count) {
            // 上傳動態(tài)照片到阿里云 完成
        }
 
    }
 
    NSLog(@"其他操作");
    for (NSNumber *num in tampArray) {
        NSLog(@"所有操作完成后的操作--->   %@\n",num);
    }
 
});

隊(duì)列組處理for循環(huán)里的異步任務(wù)

// 創(chuàng)建隊(duì)列組惋鸥，可以使多個網(wǎng)絡(luò)請求異步執(zhí)行杂穷，執(zhí)行完之后再進(jìn)行操作
dispatch_group_t group = dispatch_group_create();
//創(chuàng)建全局隊(duì)列
dispatch_queue_t queue = dispatch_get_global_queue(0, 0);
 
dispatch_group_async(group, queue, ^{
    // 循環(huán)上傳數(shù)據(jù)
    for (int i = 0; i < self.goodsArray.count; i++) {
        //創(chuàng)建dispatch_semaphore_t對象
        dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
 
        [manager POST:urlStr parameters:dict progress:nil success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {
 
            // responseObject 返回的數(shù)據(jù)
 
            // 請求成功發(fā)送信號量(+1)
            dispatch_semaphore_signal(semaphore);
 
        } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
            NSLog(@"%@",error);
            // 失敗也請求成功發(fā)送信號量(+1)
            dispatch_semaphore_signal(semaphore);
        }];
        //信號量減1，如果>0卦绣，則向下執(zhí)行亭畜，否則等待
        dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    }
});
 
// 當(dāng)所有隊(duì)列執(zhí)行完成之后
dispatch_group_notify(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
  // 執(zhí)行下面的判斷代碼
    if (state == self.goodsArray.count) {
       // 返回主線程進(jìn)行界面上的修改
        dispatch_async(dispatch_get_main_queue(), ^{
           …….
        });
    }else{
        dispatch_async(dispatch_get_main_queue(), ^{
            …..
        });
    }
});