Codable protocol for encoding/decoding in Swift - Mini Project: Build & Apply

Using Codable Protocol for Encoding and Decoding in Swift

📖 Scenario: You are building a simple app that stores information about books. You want to save this data to a file and also read it back later. Swift's Codable protocol helps you convert your data to and from a format that can be saved, like JSON.

🎯 Goal: Learn how to create a Swift struct that conforms to the Codable protocol, encode an instance to JSON data, decode JSON data back to the struct, and print the result.

📋 What You'll Learn

Create a struct called Book with properties title (String) and pages (Int)

Make Book conform to the Codable protocol

Create an instance of Book with title "Swift Programming" and pages 350

Encode the Book instance into JSON data

Decode the JSON data back into a Book instance

Print the decoded Book instance's title and pages

💡 Why This Matters

🌍 Real World

Apps often need to save user data or settings in a format like JSON. Codable makes it easy to convert Swift data to JSON and back.

💼 Career

Understanding Codable is essential for iOS developers to work with APIs, save data locally, and handle data serialization efficiently.

1

Create the Book struct conforming to Codable

Create a struct called Book with two properties: title of type String and pages of type Int. Make sure Book conforms to the Codable protocol.

Swift

# Your code here

Need a hint?

Use struct Book: Codable and add the two properties inside.

2

Create a Book instance

Create a constant called myBook and assign it a Book instance with title set to "Swift Programming" and pages set to 350.

Swift

struct Book: Codable {
    let title: String
    let pages: Int
}

# Your code here

Need a hint?

Use let myBook = Book(title: "Swift Programming", pages: 350).

3

Encode the Book instance to JSON data

Create a constant called jsonData and assign it the result of encoding myBook using JSONEncoder(). Use try? to handle errors.

Swift

struct Book: Codable {
    let title: String
    let pages: Int
}

let myBook = Book(title: "Swift Programming", pages: 350)

# Your code here

Need a hint?

Use JSONEncoder().encode(myBook) with try? to safely encode.

4

Decode JSON data and print the Book details

Decode jsonData back into a Book instance called decodedBook using JSONDecoder() and try?. Then print the title and pages of decodedBook separated by a comma and a space.

Swift

struct Book: Codable {
    let title: String
    let pages: Int
}

let myBook = Book(title: "Swift Programming", pages: 350)

let jsonData = try? JSONEncoder().encode(myBook)

# Your code here

Need a hint?

Use JSONDecoder().decode(Book.self, from: data) with try? and print the properties.