如何使用NSJSONSerialization反序列化转义的JSON字符串？ [英] How can you deserialize an escaped JSON string with NSJSONSerialization?

问题描述

我有一个iOS应用程式需要处理来自网路服务的回应。响应是包含序列化JSON对象的序列化JSON字符串，如下所示：

I have an iOS app that needs to process a response from a web service. The response is a serialized JSON string containing a serialized JSON object, looking something like this:

"{ \"name\" : \"Bob\", \"age\" : 21 }"

请注意，此响应是JSON 字符串，而不是JSON对象。我需要做的是反序列化字符串，所以我得到这个：

Note that this response is a JSON string, not a JSON object. What I need to do is deserialize the string, so that I get this:

{ "name" : "Bob", "age" : 21 }

然后我可以使用 + [NSJSONSerialization JSONObjectWithData：选项：错误：] 将反序列化为 NSDictionary 。

And then I can use +[NSJSONSerialization JSONObjectWithData:options:error:] to deserialize that into an NSDictionary.

我做第一步？也就是说，如何unes​​cape字符串，使我有一个序列化的JSON对象？ + [NSJSONSerialization JSONObjectWithData：options：error：] 仅在顶层对象是数组或字典时有效;它不适用于字符串。

But, how do I do that first step? That is, how to I "unescape" the string so that I have a serialized JSON object? +[NSJSONSerialization JSONObjectWithData:options:error:] only works if the top-level object is an array or a dictionary; it doesn't work on strings.

我最后写了我自己的JSON字符串解析器，我希望符合 RFC 4627的第2.5节。但我怀疑我忽略了一些简单的方法来使用 NSJSONSerialization 或一些其他可用的方法。

I ended up writing my own JSON string parser, which I hope conforms to section 2.5 of RFC 4627. But I suspect I've overlooked some easy way to do this using NSJSONSerialization or some other available method.

推荐答案

如果您有嵌套JSON，则只需调用 JSONObjectWithData 两次：

If you have nested JSON, then just call JSONObjectWithData twice:

NSString *string =  @"\"{ \\\"name\\\" : \\\"Bob\\\", \\\"age\\\" : 21 }\"";
// --> the string
// "{ \"name\" : \"Bob\", \"age\" : 21 }"

NSError *error;
NSString *outerJson = [NSJSONSerialization JSONObjectWithData:[string dataUsingEncoding:NSUTF8StringEncoding]
                              options:NSJSONReadingAllowFragments error:&error];
// --> the string
//  { "name" : "Bob", "age" : 21 }
NSDictionary *innerJson = [NSJSONSerialization JSONObjectWithData:[outerJson dataUsingEncoding:NSUTF8StringEncoding]
                              options:0 error:&error];
// --> the dictionary
// { age = 21; name = Bob; }

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