iphone - 如何获取 JSON 值？

Question

响应:

{
        "AT": null,
        "EMs": [
            {
                "EC": null,
                "LM": null,
                "SCs": 0,
                "SM": "Username or Password is invalid."
            }
        ],
        "OS": 1,
        "PWD": "3456",
        "UId": 399,
        "UN": "bb",
        "COM": "Apple",
        "DId": 0,
        "DN": "iPhone",
        "DOS": "iOS",
        "EA": "aa@gmail.com",
        "FN": "bb",
        "IsCon": true,
        "IsSuc": false,
        "SD": "bb",
        "SLT": "XU0QpDVC",
        "STs": 0,
        "UQId": "1d3346c",
        "US": 2,
        "Ver": "6.0"
    }

这里我想获取“用户名或密码无效”之类的 SM 标签值。

我试过这段代码

NSError *error;
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];

NSString *SMString = [json objectForKey:@"SM"];
NSString *OSString = [json objectForKey:@"OS"];
NSString *DIdString = [json objectForKey:@"DId"];
NSString *UIdString = [json objectForKey:@"UId"];

Answer 1

我希望它能工作:

NSDictionary *json = [NSJSONSerialization JSONObjectWithData:responseData
                                                     options:kNilOptions
                                                       error:&error];
NSArray *EMsArray = [json objectForKey:@"EMs"];
NSAssert([EMsArray count] > 0, @"Expected at least one element in EMs array");
NSString *SMString = [[EMsArray objectAtIndex:0] objectForKey:@"SM"];