先上方法名，該方法提供了幾個(gè)圖片縮放的預(yù)處理功能时迫，以及上傳失敗再次上傳的功能。由于我們后臺(tái)不支持修改圖片名字谓晌，就去除了圖片命名的功能掠拳。

用到的知識(shí)點(diǎn)主要是：
Http鏈接、多線程GCD

/**
 上傳多張圖片
 
 @param images 圖片數(shù)組
 @param url URL
 @param paramsDic 參數(shù)
 @param imageScale 上傳圖片縮放比例
 @param times 上傳失敗-重新上傳次數(shù)
 @param uploadImageBlock 回調(diào)函數(shù)
 */
+(void)uploadImages:(NSArray<UIImage *> *)images url:(id)url params:(id)paramsDic imageScale:(CGFloat)imageScale reConnectTimes:(NSInteger)times finishBlock:(void (^)(NSArray<NSString*> *errorStrArr, NSArray<ResModel*> *modelArr))uploadImageBlock;

下面講講主要實(shí)現(xiàn)思路：
1.先對(duì)上傳的URL路徑進(jìn)行合法性的判斷纸肉；
2.用于回調(diào)的block賦值溺欧；
3.組裝上傳接口的傳參，防止漏傳參數(shù)柏肪；
4.生成NSURLRequest的對(duì)象姐刁，設(shè)置HTTPMethod、HTTPBody烦味、TimeoutInterval聂使、host等屬性；
5.建立dispatch_group對(duì)象，用于管理請(qǐng)求（由于NSURLSessionDataTask創(chuàng)建時(shí)默認(rèn)為異步的柏靶，為了加快上傳的速度弃理，通過(guò)dispatch_group管理這些請(qǐng)求），詳見(jiàn)下面代碼：

//圖片請(qǐng)求結(jié)果
    __block NSMutableArray* resModelResultArr = [[NSMutableArray alloc]init];
    __block NSMutableArray* errorResultArr = [[NSMutableArray alloc]init];
    
    //通過(guò)dispatch_group 管理多個(gè)請(qǐng)求
    dispatch_queue_t dispatchQueue = dispatch_queue_create("uploadImageQueue", DISPATCH_QUEUE_CONCURRENT);
    dispatch_group_t dispatchGroup = dispatch_group_create();
    
    for (int i = 0; i < images.count; i++) {
        
        ResModel* model=[[ResModel alloc]init];
        model.serviceStr=paramsDic[@"service"];
        model.requestUrlStr=urlReq.URL.absoluteString;
        model.requestStr=ccstr(@"%@%@",urlReq.URL.absoluteString,paraString);
        
        dispatch_group_async(dispatchGroup, dispatchQueue, ^(){
            dispatch_group_enter(dispatchGroup);
            NSURLRequest* request = [CC_UploadImagesTool recaculateImageDatas:images[i] imageScale:imageScale paramsDic:paramsDic request:urlReq];
            
            [CC_UploadImagesTool requestSingleImageWithSession:session executorDelegate:executorDelegate request:request index:i+1 reConnectTimes:times model:model finishBlock:^(NSString *error, ResModel *resModel) {
                if (error) {
                    [errorResultArr addObject:error];
                }
                [resModelResultArr addObject:resModel];
                dispatch_group_leave(dispatchGroup);
            }];
        });
    }
    
    dispatch_group_notify(dispatchGroup, dispatch_get_main_queue(), ^(){
        NSLog(@"所有圖片上傳完成-----end");
        [session finishTasksAndInvalidate];
        executorDelegate.finishUploadImagesCallbackBlock(errorResultArr, resModelResultArr);
    });

這邊將每個(gè)請(qǐng)求封裝為單獨(dú)的一個(gè)方法宿礁，方便請(qǐng)求失敗時(shí)重新發(fā)起請(qǐng)求

+(void)requestSingleImageWithSession:(NSURLSession*)session executorDelegate:(CC_HttpTask *)executorDelegate request:(NSURLRequest*)request index:(int)index reConnectTimes:(NSInteger)reConnectTimes model:(ResModel*)model finishBlock:(void (^)(NSString *, ResModel *))block{
    
    executorDelegate.finishCallbackBlock = block; // 綁定執(zhí)行完成時(shí)的block
    
    __block NSInteger reTryTimes = reConnectTimes;
    __weak __typeof(self)weakSelf = self;
    
    NSURLSessionDataTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        __strong __typeof(self)strongSelf = weakSelf;
        if (error) {
            //重新發(fā)起請(qǐng)求
            if (reTryTimes == 0) {
                [model parsingError:error];
                executorDelegate.finishCallbackBlock(model.errorMsgStr, model);
            }else{
                NSLog(@"上傳第%d張圖片失敗-----重連還剩%ld次", index, reTryTimes);
                reTryTimes--;
                [strongSelf requestSingleImageWithSession:session executorDelegate:executorDelegate request:request index:index reConnectTimes:reTryTimes model:model finishBlock:block];
            }
        }else{
            NSDictionary *result = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];
            model.resultDic = result;
            NSLog(@"上傳第%d張圖片成功-----result:%@", index, result);
            executorDelegate.finishCallbackBlock(model.errorMsgStr, model);
        }
    }];
    [task resume];
}

下面對(duì)每個(gè)請(qǐng)求進(jìn)行封裝案铺，通過(guò)數(shù)據(jù)流的方式上傳數(shù)據(jù)蔬芥，從而避免了不知道設(shè)什么mimeType

+(NSURLRequest*)recaculateImageDatas:(UIImage*)image imageScale:(CGFloat)imageScale paramsDic:(NSDictionary*)paramsDic request:(NSMutableURLRequest*)urlReq{
    NSString *TWITTERFON_FORM_BOUNDARY = @"AaB03x";
    //分界線 --AaB03x
    NSString *MPboundary=[[NSString alloc]initWithFormat:@"--%@",TWITTERFON_FORM_BOUNDARY];
    //結(jié)束符 AaB03x--
    NSString *endMPboundary=[[NSString alloc]initWithFormat:@"%@--",MPboundary];
    //http body的字符串
    NSMutableString *body=[[NSMutableString alloc]init];
    //參數(shù)的集合的所有key的集合
    NSArray *keys= [paramsDic allKeys];
    //遍歷keys
    for(int i=0;i<[keys count];i++) {
        //得到當(dāng)前key
        NSString *key=[keys objectAtIndex:i];
        //添加分界線梆靖，換行
        [body appendFormat:@"%@\r\n",MPboundary];
        //添加字段名稱，換2行
        [body appendFormat:@"Content-Disposition: form-data; name=\"%@\"\r\n\r\n", key];
        //添加字段的值
        [body appendFormat:@"%@\r\n",[paramsDic objectForKey:key]];
    }
    //聲明myRequestData笔诵，用來(lái)放入http body
    NSMutableData *myRequestData=[NSMutableData data];
    //將body字符串轉(zhuǎn)化為UTF8格式的二進(jìn)制
    [myRequestData appendData:[body dataUsingEncoding:NSUTF8StringEncoding]];
    
    //要上傳的圖片--得到圖片的data
    NSData* data = UIImageJPEGRepresentation(image, imageScale);
    NSMutableString *imgbody = [[NSMutableString alloc] init];
    //添加分界線返吻，換行
    [imgbody appendFormat:@"%@\r\n",MPboundary];
    
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    formatter.dateFormat =@"yyyyMMddHHmmss";
    NSString *str = [formatter stringFromDate:[NSDate date]];
    NSString *fileName = [NSString stringWithFormat:@"%@.png", str];
    [imgbody appendFormat:@"Content-Disposition: form-data; name=\"image\"; filename=\"%@\"\r\n", fileName];
    //聲明上傳文件的格式
    [imgbody appendFormat:@"Content-Type: application/octet-stream; charset=utf-8\r\n\r\n"];
    //將body字符串轉(zhuǎn)化為UTF8格式的二進(jìn)制
    [myRequestData appendData:[imgbody dataUsingEncoding:NSUTF8StringEncoding]];
    //將image的data加入
    [myRequestData appendData:data];
    [myRequestData appendData:[ @"\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
    //聲明結(jié)束符：--AaB03x--
    NSString *end=[[NSString alloc]initWithFormat:@"%@\r\n",endMPboundary];
    //加入結(jié)束符--AaB03x--
    [myRequestData appendData:[end dataUsingEncoding:NSUTF8StringEncoding]];
    //設(shè)置HTTPHeader中Content-Type的值
    NSString *content=[[NSString alloc]initWithFormat:@"multipart/form-data; boundary=%@",TWITTERFON_FORM_BOUNDARY];
    //設(shè)置HTTPHeader
    [urlReq setValue:content forHTTPHeaderField:@"Content-Type"];
    //設(shè)置Content-Length
    [urlReq setValue:[NSString stringWithFormat:@"%lu", (unsigned long)[myRequestData length]] forHTTPHeaderField:@"Content-Length"];
    //設(shè)置http body
    [urlReq setHTTPBody:myRequestData];
    
    return urlReq;
}

以上就是本功能實(shí)現(xiàn)的思路及代碼。

遇到的坑：
由于我們后臺(tái)一次數(shù)據(jù)流只支持單張圖片上傳乎婿，所以沒(méi)貼多張的代碼测僵，有需要的小伙伴可以去這里

溫馨提示： 上面代碼是基于公司基礎(chǔ)庫(kù)實(shí)現(xiàn)的，所以可能非我們公司的小伙伴直接拿來(lái)用的話會(huì)報(bào)錯(cuò)谢翎，建議根據(jù)思路自己修改部分內(nèi)容