1. Request failed: unauthorized (401)

+ (NSString *)dictionaryToJSONString:(NSDictionary *)dictionary 
{
    NSError *error = nil;
    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dictionary options:NSJSONWritingPrettyPrinted error:&error];
    NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
    return jsonString;
}


+ (NSString *)arrayToJSONString:(NSArray *)array
 {
    NSError *error = nil;
    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:array options:NSJSONWritingPrettyPrinted error:&error];
    NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
}


// 字符串轉Data
NSString *str =@"jesfds"; 
NSData *data =[str dataUsingEncoding:NSUTF8StringEncoding];
// NSData轉NSString
NSString *result  =[[ NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

// data 轉char
NSData *data; 
char *test=[data bytes]; 

// char 轉data 
byte* tempData = malloc(sizeof(byte)*16); 
NSData *content=[NSData dataWithBytes:tempData length:16];

2. 3840

錯誤信息如下:

Error Domain=NSCocoaErrorDomain Code=3840 "The operation couldn’t be completed. (Cocoa error 3840.)" (JSON text did not start with array or object and option to allow fragments not set.) UserInfo=0x9152780 {NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.}

錯因：接口返回的是字符串，客戶端卻以JSON類型接收。

解決方案如下:

 sessionManager.responseSerializer = [AFHTTPResponseSerializer serializer];

3. -1016

在進行網絡請求時出現-1016 是因為只支持text/json，application/json，text/javascript。
解決方案如下：

manager.responseSerializer.acceptableContentTypes = [NSSet setWithObjects:@"text/html",@"application/json",nil];

3. code 和 statusCode

• 獲取statusCode

failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
        NSHTTPURLResponse *response = (NSHTTPURLResponse *)task.response;
        NSInteger statusCode = [response statusCode];
    }];
}