Protocol composition in Swift - Mini Project: Build & Apply

Using Protocol Composition in Swift

📖 Scenario: Imagine you are building a simple app that manages different types of users. Some users can log in, and some users can also post messages. You want to create a way to group these capabilities together using protocols.

🎯 Goal: You will create two protocols, then use protocol composition to define a type that requires both capabilities. Finally, you will create a user that conforms to both protocols and print a message showing the combined abilities.

📋 What You'll Learn

Create a protocol named Loginable with a method login() that prints "User logged in"

Create a protocol named Postable with a method postMessage() that prints "Message posted"

Create a type alias named UserActions that composes Loginable and Postable

Create a struct named User that conforms to UserActions and implements both methods

Create an instance of User and call both login() and postMessage()

Print the outputs exactly as specified

💡 Why This Matters

🌍 Real World

Protocol composition helps organize code by grouping multiple capabilities together, making it easier to write flexible and reusable code.

💼 Career

Understanding protocol composition is important for Swift developers to design clean, modular, and maintainable codebases, especially in app development.

1

Create the protocols

Create a protocol called Loginable with a method login() that prints "User logged in". Also create a protocol called Postable with a method postMessage() that prints "Message posted".

Swift

# Define protocol Loginable with method login()
# Define protocol Postable with method postMessage()

Need a hint?

Protocols define methods without implementation. Just declare the method signatures.

2

Create the protocol composition type alias

Create a type alias called UserActions that composes the protocols Loginable and Postable using protocol composition syntax.

Swift

protocol Loginable {
    func login()
}

protocol Postable {
    func postMessage()
}

# Create typealias UserActions as Loginable & Postable

Need a hint?

Use typealias UserActions = Loginable & Postable to combine protocols.

3

Create a struct conforming to the composed protocols

Create a struct called User that conforms to UserActions. Implement the login() method to print "User logged in" and the postMessage() method to print "Message posted".

Swift

protocol Loginable {
    func login()
}

protocol Postable {
    func postMessage()
}

typealias UserActions = Loginable & Postable

# Create struct User conforming to UserActions
# Implement login() and postMessage() methods

Need a hint?

Implement both methods inside the struct with the exact print statements.

4

Create an instance and call the methods

Create an instance of User named user. Call user.login() and user.postMessage() to print the messages.

Swift

protocol Loginable {
    func login()
}

protocol Postable {
    func postMessage()
}

typealias UserActions = Loginable & Postable

struct User: UserActions {
    func login() {
        print("User logged in")
    }
    func postMessage() {
        print("Message posted")
    }
}

# Create instance user and call login() and postMessage()

Need a hint?

Make sure to create the instance and call both methods exactly as shown.