如何使用可编码协议在 swift 中为同一结构使用 2 个编码键

Question

So I was searching if I have User struct that I want to use two different APIs on it

struct User {
   var firstName: String
}

first API has the key firstName , second one has the key first_Name

Answer 1

The point is to use custom decoder s not custom key codings!

The struct will stay the same for both:

struct User: Codable {
    let firstName: String
}

Camel Case Example

let firstJSON = #"{ "firstName": "Mojtaba" }"#.data(using: .utf8)!

let firstDecoder = JSONDecoder()

print(try! firstDecoder.decode(User.self, from: firstJSON))

---

Snace Case Example

let secondJSON = #"{ "first_name": "Mojtaba" }"#.data(using: .utf8)!

let secondDecoder: JSONDecoder = {
    let decoder =  JSONDecoder()
    decoder.keyDecodingStrategy = .convertFromSnakeCase
    return decoder
}()

print(try! secondDecoder.decode(User.self, from: secondJSON))

_{Also, You can implement your own custom strategy.}

So decide which decoder (or decoding strategy) you need for each API.

Answer 2

A neglected approach is a custom keyDecodingStrategy , however this requires a dummy CodingKey struct.

struct AnyKey: CodingKey {
    var stringValue: String
    var intValue: Int?
    
    init?(stringValue: String) { self.stringValue = stringValue }
    init?(intValue: Int) { self.stringValue = String(intValue) }
}

let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .custom({
    let currentKey = $0.last!
    if currentKey.stringValue == "first_Name" {
        return AnyKey(stringValue: "firstName")!
    } else {
        return currentKey
    }
})