Capture lists in closures in Swift - Mini Project: Build & Apply

Capture Lists in Closures

📖 Scenario: Imagine you are creating a simple Swift program that uses closures to remember values. Closures can capture variables from their surroundings. Sometimes, you want to control how these variables are captured to avoid unexpected changes.

🎯 Goal: You will build a Swift program that demonstrates how to use a capture list in a closure to keep a fixed value, even if the original variable changes later.

📋 What You'll Learn

Create a variable called number with the value 10

Create a closure called closure that captures number using a capture list

Change the value of number to 20 after the closure is created

Call the closure and print its result to show the captured value

💡 Why This Matters

🌍 Real World

Capture lists in closures are useful when you want to keep a snapshot of data at a certain moment, such as in UI event handlers or asynchronous code.

💼 Career

Understanding capture lists helps you write safer Swift code that avoids unexpected side effects, a valuable skill for iOS and macOS developers.

1

Create the initial variable

Create a variable called number and set it to 10.

Swift

# Your code here

Need a hint?

Use var number = 10 to create the variable.

2

Create a closure with a capture list

Create a closure called closure that captures number using a capture list to keep its current value.

Swift

var number = 10
// Your code here

Need a hint?

Use { [number] in return number } to capture number by value.

3

Change the variable after closure creation

Change the value of number to 20 after the closure is created.

Swift

var number = 10
let closure = { [number] in
    return number
}
// Your code here

Need a hint?

Simply assign number = 20 after the closure.

4

Call the closure and print the result

Call the closure closure() and print its result using print().

Swift

var number = 10
let closure = { [number] in
    return number
}
number = 20
// Your code here

Need a hint?

Use print(closure()) to show the captured value.