JSON to Swift Codable

Swift Codable Protocol

Codable is Swift's type-safe serialization protocol. It combines Encodable and Decodable, enabling you to convert between Swift types and JSON with minimal code.

import Foundation

struct User: Codable {
    let id: Int
    let name: String
    let isActive: Bool

    enum CodingKeys: String, CodingKey {
        case id
        case name
        case isActive = "is_active"
    }
}

Decoding JSON with JSONDecoder

import Foundation

let jsonData = """
{"id": 1, "name": "Alice", "is_active": true}
""".data(using: .utf8)!

let decoder = JSONDecoder()
let user = try! decoder.decode(User.self, from: jsonData)
print(user.name) // Alice

// Encoding back to JSON
let encoder = JSONEncoder()
encoder.outputFormatting = .prettyPrinted
let encoded = try! encoder.encode(user)
print(String(data: encoded, encoding: .utf8)!)

Common Use Cases

• iOS Apps: Model REST API responses in Swift apps with URLSession
• macOS Apps: Parse configuration files or API data
• SwiftUI: Data models for @State and @ObservableObject
• Combine: Decode publishers from network requests
• Core Data: Map JSON to Core Data entities

FAQ