Why property wrappers reduce boilerplate in Swift - See It in Action

Why property wrappers reduce boilerplate

📖 Scenario: Imagine you are building a simple app that needs to store and validate user input, like a username. You want to make sure the username is always trimmed of spaces and never empty. Doing this repeatedly in your code can be boring and error-prone.

🎯 Goal: You will create a property wrapper in Swift that automatically trims whitespace from a string and ensures it is not empty. This will help you avoid writing the same trimming and validation code every time you use a username property.

📋 What You'll Learn

Create a property wrapper called Trimmed that trims whitespace from a string

Create a struct called User with a property username using the @Trimmed wrapper

Initialize a User instance with a username containing spaces

Print the trimmed username to show the property wrapper works

💡 Why This Matters

🌍 Real World

Property wrappers are used in apps to simplify data validation, formatting, and storage, reducing repeated code and bugs.

💼 Career

Understanding property wrappers is important for Swift developers to write clean, reusable, and maintainable code in iOS and macOS projects.

1

Create the Trimmed property wrapper

Create a property wrapper called Trimmed that has a wrappedValue of type String. Initialize it with a string and trim whitespace from the start and end using trimmingCharacters(in: .whitespaces).

Swift

# Create the property wrapper called Trimmed
// Your code here

Need a hint?

Use @propertyWrapper before the struct. Implement wrappedValue with get and set that trims whitespace.

2

Create the User struct with a @Trimmed username

Create a struct called User with a property username of type String that uses the @Trimmed property wrapper.

Swift

@propertyWrapper
struct Trimmed {
    private var value: String

    var wrappedValue: String {
        get { value }
        set { value = newValue.trimmingCharacters(in: .whitespaces) }
    }

    init(wrappedValue: String) {
        self.value = wrappedValue.trimmingCharacters(in: .whitespaces)
    }
}

// Create the User struct with a @Trimmed username property
// Your code here

Need a hint?

Define struct User with a property username using @Trimmed.

3

Initialize a User with a spaced username

Create a variable called user and initialize it with User(username: " swiftLearner ").

Swift

@propertyWrapper
struct Trimmed {
    private var value: String

    var wrappedValue: String {
        get { value }
        set { value = newValue.trimmingCharacters(in: .whitespaces) }
    }

    init(wrappedValue: String) {
        self.value = wrappedValue.trimmingCharacters(in: .whitespaces)
    }
}

struct User {
    @Trimmed var username: String
}

// Create a user with username "  swiftLearner  "
// Your code here

Need a hint?

Create a variable user and assign User(username: " swiftLearner ")

4

Print the trimmed username

Write a print statement to display user.username.

Swift

@propertyWrapper
struct Trimmed {
    private var value: String

    var wrappedValue: String {
        get { value }
        set { value = newValue.trimmingCharacters(in: .whitespaces) }
    }

    init(wrappedValue: String) {
        self.value = wrappedValue.trimmingCharacters(in: .whitespaces)
    }
}

struct User {
    @Trimmed var username: String
}

var user = User(username: "  swiftLearner  ")

// Print the trimmed username
// Your code here

Need a hint?

Use print(user.username) to show the trimmed username.