iOS多张图片总是只能上传一张的问题

最近在做图片上传的功能，使用的AFNetworking提供的方法上传图片，发现多张图片时总是只有一张图片上传到后台。

有问题的上传代码为：

特别提醒：

创建AFHTTPsessionManager时，直接使用[AFHTTPSessionManager manager]会造成内存泄漏，需要实现单列方法，可参看AFNetworking的Demo

        AFHTTPSessionManager *manager = [TPHTTPTool sharedHTTPManager];        manager.responseSerializer = [AFJSONResponseSerializer serializer];        //设置响应头可以接收的content-type        NSMutableSet *tempSet = [manager.responseSerializer.acceptableContentTypes mutableCopy];        [tempSet addObjectsFromArray:@[@"text/html"]];        manager.responseSerializer.acceptableContentTypes = [tempSet copy];        [manager POST:URL_detailPatientUpdate parameters:params constructingBodyWithBlock:^(id<AFMultipartFormData>  _Nonnull formData) {            for(NSInteger i = 0; i < images.count; i++){                //取出单张图片二进制数据                id obj = images[i];                UIImage *image = nil;                if ([obj isKindOfClass:[UIImage class]]) {                    image = (UIImage *)obj;                }else{                    image = [UIImage imageWithContentsOfFile:obj];                }                if (image) {                    NSData *imageData = [TPDataTool dataWithImage:image maxKB:500.0f];                    NSLog(@"图片大小:%ld K" , (long)imageData.length / 1024);                    // 上传filename                    NSString *fileName = [NSString stringWithFormat:@"image_%ld.jpg", (long)blockI];                    [formData appendPartWithFileData:imageData name:@"file" fileName:fileName mimeType:@"image/jpeg"];                }            }        } PRogress:^(NSProgress * _Nonnull uploadProgress) {                    } success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responSEObject) {                    } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {                    }];
找后台调试后发现，通过上面的方法上传多张图片，实际上只有一张被传到后台，可能的原因是：
上传多张图片时，由于url的参数没有变化，iOS默认是同一个请求，只发送了一次请求给后台，故后台只收到一张图片。
解决办法是将循环把整个请求方法都包起来。代码为：
// 上传多张图片    for(NSInteger i = 0; i < images.count; i++)    {        AFHTTPSessionManager *manager = [TPHTTPTool sharedHTTPManager];        manager.responseSerializer = [AFJSONResponseSerializer serializer];        //设置响应头可以接收的content-type        NSMutableSet *tempSet = [manager.responseSerializer.acceptableContentTypes mutableCopy];        [tempSet addObjectsFromArray:@[@"text/html"]];        manager.responseSerializer.acceptableContentTypes = [tempSet copy];        __block NSInteger blockI = i;        [manager POST:URL_detailPatientUpdate parameters:params constructingBodyWithBlock:^(id<AFMultipartFormData>  _Nonnull formData) {            //取出单张图片二进制数据            id obj = images[blockI];            UIImage *image = nil;            if ([obj isKindOfClass:[UIImage class]]) {                image = (UIImage *)obj;            }else{                image = [UIImage imageWithContentsOfFile:obj];            }            if (image) {                NSData *imageData = [TPDataTool dataWithImage:image maxKB:500.0f];                NSLog(@"图片大小:%ld K" , (long)imageData.length / 1024);                // 上传filename                NSString *fileName = [NSString stringWithFormat:@"image_%ld.jpg", (long)blockI];                [formData appendPartWithFileData:imageData name:@"file" fileName:fileName mimeType:@"image/jpeg"];            }        } progress:^(NSProgress * _Nonnull uploadProgress) {                    } success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {                    } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {                   }];}