展开字典数组 [英] Unwrap array of dictionary

问题描述

我有一个来自 firebase 的字典数组，如下所示:

"gcm.notification.data" = "{\"request\":\"update_location\",\"latitude\":\"45.48945419494574\",\"customMessage\":{\"loc-args\":[\"iPhone di Tester\"],\"loc-key\":\"LOCATION_CHECKIN\"},\"type\":\"checkin\",\"message\":\"Ggg\",\"经度\":\"9.195329826333742\",\"child\":{\"name\":\"iPhone di Tester\",\"pid\":\"C312EDDC-E8A8-4EFC-9E65-957BE5DAC5FC\"}}";

我试图解开请求，如下所示，但它崩溃了，谁能帮忙.

 NSDictionary *gcmnotificationdat = [userInfo objectForKey:@"gcm.notification.data"];NSString *request = [gcmnotificationdat objectForKey:@"request"];

解决方案

您遇到了崩溃.作为开发人员，阅读它很重要.你看懂也可以不看，但是你肯定可以去找，这个是比较有名的.这是任何 iOS 开发人员都应该知道的基本崩溃消息.如果没有，请与我们分享.您将有更好的机会获得答案.

最重要的部分是:

-[__NSCFConstantString objectForKey:]:无法识别的选择器发送到实例 0x100002090

这意味着您正在尝试在 NSString 对象上调用方法 objectForKey:.NSString 不知道，这就是它崩溃的原因.

key gcm.notification.data 的值是一个 JSON Stringified.

所以 [userInfo objectForKey:@"gcm.notification.data"]; 实际上是一个 NSString 而不是 NSDictionary.>

让我们现在修复它:

//为了测试而创建样本NSDictionary *userInfo = @{@"gcm.notification.data": @"{\"request\":\"update_location\",\"latitude\":\"45.48945419494574\",\"customMessage\":{\"loc-args\":[\"iPhone di Tester\"],\"loc-key\":\"LOCATION_CHECKIN\"},\"type\":\"checkin\",\"message\":\"Ggg\",\"longitude\":\"9.195329826333742\",\"child\":{\"name\":\"iPhone di Tester\",\"pid\":\"C312EDDC-E8A8-4EFC-9E65-957BE5DAC5FC\"}}"};//解析NSString *gcmNotificationJSONString = [userInfo objectForKey:@"gcm.notification.data"];NSData *gcmNotificationJSONData = [gcmNotificationJSONString dataUsingEncoding:NSUTF8StringEncoding];NSDictionary *gcmNotification = [NSJSONSerialization JSONObjectWithData:gcmNotificationJSONData options:0 error:nil];NSString *request = [gcmNotification objectForKey:@"request"];NSLog(@"请求:%@", request);

注意:我删除了您使用的 var 名称的dat"部分，因为键以data"结尾，以免混淆 NSString、NSData 和 NSDictionary 因为我从类中明确命名它们.我在评论中打错了一个类，小心并从这里的代码中修复它.

I have an array of dictionary from firebase like bellow :

"gcm.notification.data" = "{\"request\":\"update_location\",\"latitude\":\"45.48945419494574\",\"customMessage\":{\"loc-args\":[\"iPhone di Tester\"],\"loc-key\":\"LOCATION_CHECKIN\"},\"type\":\"checkin\",\"message\":\"Ggg\",\"longitude\":\"9.195329826333742\",\"child\":{\"name\":\"iPhone di Tester\",\"pid\":\"C312EDDC-E8A8-4EFC-9E65-957BE5DAC5FC\"}}";

I tried to unwrap the request, like bellow but it crash, can anyone help.

 NSDictionary *gcmnotificationdat = [userInfo objectForKey:@"gcm.notification.data"];
    NSString *request = [gcmnotificationdat objectForKey:@"request"];

解决方案

You got a crash. As a developer it's important to read it. You can either understand it or not, but you can certainly look for it, and this one is quite known. It's a basic crash message that any iOS developer should know. If you don't, share it with us. You'll get better chances to get answers.

The most important part being:

-[__NSCFConstantString objectForKey:]: unrecognized selector sent to instance 0x100002090

It means that you are trying to call a method objectForKey: on a NSString object. NSString doesn't know it, and that's why it crashes.

The value of key gcm.notification.data is a JSON Stringified.

So [userInfo objectForKey:@"gcm.notification.data"]; is in fact a NSString not a NSDictionary.

Let's fix it now:

//Creation of the sample for the sake of the test
NSDictionary *userInfo = @{@"gcm.notification.data": @"{\"request\":\"update_location\",\"latitude\":\"45.48945419494574\",\"customMessage\":{\"loc-args\":[\"iPhone di Tester\"],\"loc-key\":\"LOCATION_CHECKIN\"},\"type\":\"checkin\",\"message\":\"Ggg\",\"longitude\":\"9.195329826333742\",\"child\":{\"name\":\"iPhone di Tester\",\"pid\":\"C312EDDC-E8A8-4EFC-9E65-957BE5DAC5FC\"}}"};

//Parsing
NSString *gcmNotificationJSONString = [userInfo objectForKey:@"gcm.notification.data"];
NSData *gcmNotificationJSONData = [gcmNotificationJSONString dataUsingEncoding:NSUTF8StringEncoding];
NSDictionary *gcmNotification = [NSJSONSerialization JSONObjectWithData:gcmNotificationJSONData options:0 error:nil];
NSString *request = [gcmNotification objectForKey:@"request"];
NSLog(@"Request: %@", request);

Note: I removed the "dat" part of the var names, that you used because the key ends with "data" to not confuse NSString, NSData and NSDictionary as I explicitly named them from the class. I mistype a class in the comment, be careful and fix it from the code here.

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