Protocol with associated types in Swift - Mini Project: Build & Apply

Using Protocol with Associated Types in Swift

📖 Scenario: Imagine you are building a simple app that manages different types of containers, like boxes or bags, each holding items of a specific type.

🎯 Goal: You will create a protocol with an associated type to represent a container, then implement this protocol for a specific container type, and finally display the contents.

📋 What You'll Learn

Create a protocol called Container with an associated type named Item

Add a property items of type array of Item in the protocol

Create a struct called Box that conforms to Container and holds String items

Add a variable box of type Box with some string items

Print the items inside the box

💡 Why This Matters

🌍 Real World

Protocols with associated types let you write code that works with many kinds of data containers, like lists, stacks, or queues, each holding different item types.

💼 Career

Understanding protocols with associated types is important for Swift developers building flexible and reusable components in apps.

1

Create the Container protocol with an associated type

Write a protocol called Container with an associated type named Item. Inside the protocol, declare a property items of type array of Item that is gettable and settable.

Swift

# Write the protocol Container with associatedtype Item and property items
# Your code here

Need a hint?

Use associatedtype Item inside the protocol to define a placeholder type.

2

Create a struct Box that conforms to Container with String items

Create a struct called Box that conforms to the Container protocol. Inside Box, declare a variable items of type array of String.

Swift

protocol Container {
    associatedtype Item
    var items: [Item] { get set }
}

// Create struct Box conforming to Container with String items
# Your code here

Need a hint?

Make sure Box declares items as [String] to satisfy the protocol.

3

Create a variable box of type Box with some string items

Create a variable called box of type Box and initialize it with the items ["apple", "banana", "cherry"].

Swift

protocol Container {
    associatedtype Item
    var items: [Item] { get set }
}

struct Box: Container {
    var items: [String]
}

// Create variable box with items ["apple", "banana", "cherry"]
# Your code here

Need a hint?

Use the memberwise initializer of Box to set the items.

4

Print the items inside the box

Write a print statement to display the items property of the box variable.

Swift

protocol Container {
    associatedtype Item
    var items: [Item] { get set }
}

struct Box: Container {
    var items: [String]
}

var box = Box(items: ["apple", "banana", "cherry"])

// Print the items inside box
# Your code here

Need a hint?

Use print(box.items) to show the contents.