ProperyWrapper decode

Test.playground

import UIKit

let jsonString =
"""
{
"name": "Tim",
"age": "28"
}
"""

@propertyWrapper
struct Age: Codable {
    var age: Int = 0
    var wrappedValue: Int {
        get {
            return age
        }
        
        set {
            age = newValue * 10
        }
    }
}

struct People: Codable {
    var name: String
    @Age var age: Int
}

extension People {
    init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        
        name = try values.decode(String.self, forKey: .name)
        age = Int(try values.decode(String.self, forKey: .age)) ?? 0
    }
}

let jsonData = jsonString.data(using: .utf8)!
let user = try! JSONDecoder().decode(People.self, from: jsonData)
print(user.name)
print(user.age)