一、在自己封装的AFNetWorking中添加移除null的字段

//需要在网络请求中添加的字段
 AFJSONResponseSerializer *response = [AFJSONResponseSerializer serializer];
 response.removesKeysWithNullValues = YES;   
 manager.responseSerializer = response;

+ (void)be_basePOSTRequestModel:(BEBaseRequestModel *)model url:(NSString *)url finishBlock:(FinishBlcok)finishBlock {
    NSLog(@"requestDict = %@",model.keyValues);
    NSLog(@"requestUrl = %@",url);
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
    NSString *utf = [url stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    AFHTTPSessionManager * manager = [AFHTTPSessionManager manager];
    manager.requestSerializer = [AFHTTPRequestSerializer serializer];
    manager.requestSerializer.timeoutInterval = 20;
    manager.responseSerializer.acceptableContentTypes = [NSSet setWithObjects:@"text/html",@"application/json", @"text/json", nil];
    AFJSONResponseSerializer *response = [AFJSONResponseSerializer serializer];
    response.removesKeysWithNullValues = YES;
    manager.responseSerializer = response;
    [manager POST:utf parameters:model.keyValues progress:^(NSProgress * _Nonnull uploadProgress) {
        
    } success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {
        
        debugLog(@"responseObject = %@", responseObject);
        [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
        NSDictionary *JSON = nil;
        if(responseObject != nil){
            if ([responseObject isKindOfClass:[NSDictionary class]]) {
                JSON = responseObject;
            }else {
                JSON = [NSJSONSerialization JSONObjectWithData:responseObject options:kNilOptions error:nil];
                NSLog(@"posT response: %@", JSON);
            }
            finishBlock(JSON,nil);
        }

    } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
        NSLog(@"error = %@",error);
        [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
        finishBlock(nil,error);
        [self showError:error.localizedDescription];
    }];
}

二、在AFNetWorking源代码中修改

static id AFJSONObjectByRemovingKeysWithNullValues(id JSONObject, NSJSONReadingOptions readingOptions) {
    if ([JSONObject isKindOfClass:[NSArray class]]) {
        NSMutableArray *mutableArray = [NSMutableArray arrayWithCapacity:[(NSArray *)JSONObject count]];
        for (id value in (NSArray *)JSONObject) {
            [mutableArray addObject:AFJSONObjectByRemovingKeysWithNullValues(value, readingOptions)];
        }
        return (readingOptions & NSJSONReadingMutableContainers) ? mutableArray : [NSArray arrayWithArray:mutableArray];
    } else if ([JSONObject isKindOfClass:[NSDictionary class]]) {
        NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionaryWithDictionary:JSONObject];
        for (id <NSCopying> key in [(NSDictionary *)JSONObject allKeys]) {
            id value = (NSDictionary *)JSONObject[key];
            if (!value || [value isEqual:[NSNull null]]) {
                [mutableDictionary setObject:@"" forKey:key];
            } else if ([value isKindOfClass:[NSArray class]] || [value isKindOfClass:[NSDictionary class]]) {
                 //需要把所对应的null值替换为@""
                mutableDictionary[key] = AFJSONObjectByRemovingKeysWithNullValues(value, readingOptions);
            }
        }

        return (readingOptions & NSJSONReadingMutableContainers) ? mutableDictionary : [NSDictionary dictionaryWithDictionary:mutableDictionary];
    }

    return JSONObject;
}