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 应用程序需要处理来自网络服务的响应.响应是一个包含序列化 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，以便我得到这个:

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:options:error:] 将其反序列化为 NSDictionary.

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

但是，我该怎么做第一步呢?也就是说，我如何逃脱"?字符串以便我有一个序列化的 JSON 对象?+[NSJSONSerialization JSONObjectWithData:options:error:] 仅当顶级对象是数组或字典时才有效；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.

我最终编写了我自己的 JSON 字符串解析器，我希望它符合 RFC 4627 的第 2.5 节.但我怀疑我忽略了一些使用 NSJSONSerialization 或其他一些可用方法来做到这一点的简单方法.

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

如果你有嵌套的 JSON，那么只需调用 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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