Reference sharing and side effects in Swift - Mini Project: Build & Apply

Swift Arrays: Copy-on-Write and No Side Effects

📖 Scenario: Imagine you have a list of favorite fruits that you share with a friend by assigning the array. See what happens when the friend adds a new fruit to the list.

🎯 Goal: You will create a list of fruits, assign it to another variable, add to one, then print both to show how mutations behave with Swift arrays.

📋 What You'll Learn

Create a variable called fruits with an array of strings: ["Apple", "Banana", "Cherry"]

Create a variable called friendFruits and assign it to fruits

Add the string "Date" to friendFruits

Print both fruits and friendFruits to show their contents

💡 Why This Matters

🌍 Real World

Understanding how data is shared or copied helps avoid bugs when multiple parts of a program use the same data.

💼 Career

Many programming jobs require managing data carefully to prevent unexpected changes and bugs, especially when working with collections.

1

Create the initial fruits array

Create a variable called fruits and set it to the array ["Apple", "Banana", "Cherry"].

Swift

# Create a variable called fruits with the array ["Apple", "Banana", "Cherry"]

Need a hint?

Use var fruits = ["Apple", "Banana", "Cherry"] to create the array.

2

Assign the fruits array to friendFruits

Create a variable called friendFruits and assign it to the existing fruits variable.

Swift

var fruits = ["Apple", "Banana", "Cherry"]
# Create friendFruits and assign it to fruits

Need a hint?

Use var friendFruits = fruits to share the array.

3

Add a new fruit to friendFruits

Add the string "Date" to the friendFruits array using the append method.

Swift

var fruits = ["Apple", "Banana", "Cherry"]
var friendFruits = fruits
# Add "Date" to friendFruits

Need a hint?

Use friendFruits.append("Date") to add the new fruit.

4

Print both fruits and friendFruits

Print both fruits and friendFruits using two separate print statements to show their contents.

Swift

var fruits = ["Apple", "Banana", "Cherry"]
var friendFruits = fruits
friendFruits.append("Date")
# Print fruits and friendFruits

Need a hint?

Use print(fruits) and print(friendFruits) to show the arrays.