Parse JSON string inside another JSON-CodePudding

I have some JSON that contains another JSON object inside in a form of a string (note quotes around the "jsonString" value):

{
  "jsonString":"{\"someKey\": \"Some value\"}"
}

I know that if "jsonString" didn't have quotes around its value, I would do something like this:

import Foundation

struct Something: Decodable {
  struct SomethingElse: Decodable {
    let someKey: String
  }
  let jsonString: SomethingElse
}

let jsonData = """
               {
                 "jsonString":"{\"someKey\": \"Some value\"}"
               }
               """.data(using: .utf8)!
let something = try! JSONDecoder().decode(Something.self, from: jsonData)

But it doesn't work for my case. It doesn't work even if I treat "jsonString" as a String and do something like this:

init(from decoder: Decoder) throws {
  let container = try decoder.container(keyedBy: SomethingKey.self)

  let jsonStringString = try container.decode(String.self, forKey: .jsonString)
  if let jsonStringData = jsonStringString.data(using: .utf8) {
    self.jsonString = try JSONDecoder().decode(SomethingElse.self, from: jsonStringData)
  } else {
    self.jsonString = SomethingElse(someKey: "")
  }
}
private enum SomethingKey: String, CodingKey {
  case jsonString
}

The error I'm experiencing is:

Swift.DecodingError.dataCorrupted(Swift.DecodingError.Context(codingPath: [], debugDescription: "The given data was not valid JSON.", underlyingError: Optional(Error Domain=NSCocoaErrorDomain Code=3840 "Badly formed object around line 2, column 18." UserInfo={NSDebugDescription=Badly formed object around line 2, column 18., NSJSONSerializationErrorIndex=20})))

However, all JSON validators I tried say that the JSON is valid and conforms to RFC 8259.

Swift doesn't let me to escape nested "{" and ”}" either.

The JSON format, unfortunately, is out of my control and I cannot alter it.

I also found this question, which looks similar, but nothing there works. Answers are relevant only for regular nested JSON objects. Or I missed something.

Any help is appreciated!

CodePudding user response：

The error is saying that the whole JSON isn't valid, not just the jsonString value.

While it's true that (you can test it in online validator like JSONLint for instance):

{
    "jsonString": "{\"someKey\": \"Some value\"}"
}

When declaring it as a String in Swift, you need to make sure that the backslashes are really present.

So it's:

let jsonString = """
{ "jsonString": "{\\"someKey\\": \\"Some value\\"}"}
"""

let jsonString = #"{"jsonString":"{\"someKey\": \"Some value\"}"}"#