Codable.swift

import Foundation
import UIKit

let json = """
{
"firstname": "shakti",
"lastname": "prakash",
"age":25
}
"""

let jsonData = Data(json.utf8)

struct User:Codable {
    var firstname:String
    var lastname:String
    var age:Int
}

let decoder = JSONDecoder()

do {
   let response = try decoder.decode(User.self, from: jsonData)
    print(response)
} catch {
    print("Parsing Failed")
}