使用objective-c从json中检索值

Question

我目前正在尝试使用json和objective-c但是有点困难.以下是返回的json

{
    sethostname =     (
    {
        msgs = "Updating Apache configuration\nUpdating cPanel license...Done. Update succeeded.\nBuilding global cache for cpanel...Done";
        status = 1;
        statusmsg = "Hostname Changed to: a.host.name.com";
        warns =             (
        );
    });
}

我能够检查响应是否会返回并且密钥是sethostname但是无论我尝试什么,我都无法获得例如status或statusmsg的值.任何人都可以指出我在正确的位置.以下是我用来检查是否返回sethostname的基本代码.

NSError *myError = nil;
NSDictionary *res = [NSJSONSerialization JSONObjectWithData:response options:NSJSONReadingMutableLeaves error:&myError];
NSLog([res description]);
NSArray *arr;
arr = [res allKeys];
if ([arr containsObject:@"sethostname"])
{
    NSLog(@"worked");
}

Answer 1

如有疑问,请记下JSON数据的结构.例如:

{
    sethostname =     (
    {
        msgs = "Updating Apache configuration\nUpdating cPanel license...Done. Update succeeded.\nBuilding global cache for cpanel...Done";
        status = 1;
        statusmsg = "Hostname Changed to: a.host.name.com";
        warns =             (
        );
    });
}

(实际上是NeXTSTEP属性列表格式)意味着你有一个顶级字典.此顶级字典包含一个名为sethostname其数组的键.这个数组由字典组成,每个字典都有一组键:msgs, status, statusmsg, warns.msgs有一个字符串值,status有一个数值,statusmsg有一个字符串值,警告`有一个数组值:

dictionary (top-level)
    sethostname (array of dictionaries)
        dictionary (array element)
            msgs (string)
            status (number)
            statusmsg (string)
            warns (array)
                ??? (array element)

理解了这个结构后,您的代码应如下所示:

NSError *myError = nil;
NSDictionary *res = [NSJSONSerialization JSONObjectWithData:response options:NSJSONReadingMutableLeaves error:&myError];

if (!res) { // JSON parser failed }

// dictionary (top-level)
if (![res isKindOfClass:[NSDictionary class]]) {
    // JSON parser hasn't returned a dictionary
}

// sethostname (array of dictionaries)
NSArray *setHostNames = [res objectForKey:@"sethostname"];

// dictionary (array element)
for (NSDictionary *setHostName in setHostNames) {
    // status (number)
    NSNumber *status = [setHostName objectForKey:@"status"];

    // statusmsg (string)
    NSString *statusmsg = [setHostName objectForKey:@"statusmsg"];

    …
}