Codable and JSON

import Foundation
struct User: Codable {
    var name: String
    var age: Int
}
let user = User(name: "Nina", age: 29)
let data = try! JSONEncoder().encode(user)
print(String(data: data, encoding: .utf8)!)

import Foundation
struct User: Codable {
    var name: String
    var age: Int
}
let json = "{\"name\":\"Leo\",\"age\":34}"
let data = json.data(using: .utf8)!
let decoded = try! JSONDecoder().decode(User.self, from: data)
print("\(decoded.name) is \(decoded.age)")

1. Forgetting a type must conform to Codable (or Encodable/Decodable) before JSONEncoder/JSONDecoder can process it.
2. Assuming property names in JSON always match Swift property names exactly; mismatches require a custom CodingKeys enum.
3. Forgetting JSONEncoder().encode(_:) and JSONDecoder().decode(_:from:) are both throwing functions requiring try.

• A type conforming to Codable (both Encodable and Decodable) can be automatically converted to and from JSON.
• JSONEncoder().encode(_:) turns a Codable value into Data containing JSON.
• JSONDecoder().decode(_:from:) parses Data back into a Swift type.
• CodingKeys lets you customize how property names map to JSON keys.