In-out parameters for mutation in Swift - Mini Project: Build & Apply

In-out Parameters for Mutation in Swift

📖 Scenario: You are working on a simple app that manages a user's bank account balance. Sometimes, you need to update the balance by adding or subtracting money directly.

🎯 Goal: Build a Swift program that uses an inout parameter to change the bank account balance inside a function.

📋 What You'll Learn

Create a variable called balance with the value 1000

Create a constant called depositAmount with the value 250

Write a function called deposit that takes an inout parameter named accountBalance of type Int and a parameter amount of type Int

Inside the function deposit, add amount to accountBalance

Call the function deposit passing balance as an inout argument and depositAmount as the amount

Print the updated balance

💡 Why This Matters

🌍 Real World

Banking apps and financial software often need to update account balances safely and clearly. Using <code>inout</code> parameters helps functions change values directly.

💼 Career

Understanding how to use <code>inout</code> parameters is important for Swift developers working on apps that manage data that changes, such as user profiles, game scores, or financial records.

1

Create the initial balance and deposit amount

Create a variable called balance and set it to 1000. Then create a constant called depositAmount and set it to 250.

Swift

// Create a variable called balance and set it to 1000
// Create a constant called depositAmount and set it to 250
// Your code here

Need a hint?

Use var for balance because it will change. Use let for depositAmount because it stays the same.

2

Write the deposit function with an inout parameter

Write a function called deposit that takes an inout parameter named accountBalance of type Int and a parameter amount of type Int. Inside the function, add amount to accountBalance.

Swift

var balance = 1000
let depositAmount = 250

// Write the deposit function with inout parameter here
// Your code here

Need a hint?

Remember to use inout before the parameter type to allow mutation inside the function.

3

Call the deposit function to update balance

Call the function deposit passing balance as an inout argument and depositAmount as the amount.

Swift

var balance = 1000
let depositAmount = 250

func deposit(accountBalance: inout Int, amount: Int) {
    accountBalance += amount
}

// Call the deposit function here
// Your code here

Need a hint?

Use & before balance when passing it to the inout parameter.

4

Print the updated balance

Write a print statement to display the updated value of balance.

Swift

var balance = 1000
let depositAmount = 250

func deposit(accountBalance: inout Int, amount: Int) {
    accountBalance += amount
}

deposit(accountBalance: &balance, amount: depositAmount)

// Print the updated balance here
// Your code here

Need a hint?

Use print(balance) to show the new balance.