Swift 4 Codable decoding json

Question

I\'m trying to implement the new Codable protocol, so I added Codable to my struct, but am stuck on decoding the JSON.

Here\'s

Answer 1

You're getting this error because your JSON is likely structured as so:

{
  "themes": [
    { "title": ..., "question": ..., "answer": ... },
    { "title": ..., "question": ..., "answer": ... },
    { ... }
  ],
  ...
}

However, the code you wrote expects a [Question] at the top level. What you need is a different top-level type that has a themes property which is a [Question]. When you decode that top-level type, your [Question] will be decoded for the themes key.

Answer 2

If your JSON has a structure

{"themes" : [{"title": "Foo", "answer": 1, "question": 2},
             {"title": "Bar", "answer": 3, "question": 4}]}

you need an equivalent for the themes object. Add this struct

struct Theme : Codable {
    var themes : [Question]
}

Now you can decode the JSON:

if let decoded = try? JSONDecoder().decode(Theme.self, from: data) {
    print("decoded:", decoded)
} else {
    print("Not working")
}

The containing Question objects are decoded implicitly.

Answer 3

Hello @all I have added the code for JSON Encoding and Decoding for Swift 4.

Please use the link here