Throwing functions with throws in Swift - Mini Project: Build & Apply

Throwing functions with throws

📖 Scenario: Imagine you are building a simple app that checks if a password is strong enough. If the password is too short, the app should tell the user with an error.

🎯 Goal: You will create a throwing function that checks password length and throws an error if the password is too short. Then you will call this function and handle the error.

📋 What You'll Learn

Create an enum called PasswordError that conforms to Error with a case tooShort

Create a throwing function called checkPassword that takes a String parameter password

Inside checkPassword, throw PasswordError.tooShort if the password length is less than 8

Call checkPassword inside a do-catch block with the password "abc123"

Print "Password is strong enough" if no error is thrown

Print "Password is too short" if PasswordError.tooShort is caught

💡 Why This Matters

🌍 Real World

Throwing functions are used in apps to handle unexpected problems like invalid input or failed network calls. This helps apps respond gracefully instead of crashing.

💼 Career

Understanding how to write and handle throwing functions is important for Swift developers to build robust and user-friendly applications.

1

Create the PasswordError enum

Create an enum called PasswordError that conforms to Error with a case called tooShort.

Swift

# Your code here

Need a hint?

Use enum PasswordError: Error { case tooShort } to define the error type.

2

Create the throwing function checkPassword

Create a throwing function called checkPassword that takes a String parameter named password. Inside the function, throw PasswordError.tooShort if password.count is less than 8.

Swift

enum PasswordError: Error {
    case tooShort
}

# Your code here

Need a hint?

Define the function with throws and use throw PasswordError.tooShort inside an if check.

3

Call checkPassword inside a do-catch block

Write a do-catch block that calls checkPassword with the password "abc123". In the do block, call checkPassword("abc123"). In the catch block, catch PasswordError.tooShort specifically.

Swift

enum PasswordError: Error {
    case tooShort
}

func checkPassword(_ password: String) throws {
    if password.count < 8 {
        throw PasswordError.tooShort
    }
}

# Your code here

Need a hint?

Use do { try checkPassword("abc123") ... } catch PasswordError.tooShort { ... } to handle the error.

4

Print the result

Run the program to print the result of the password check. The output should be "Password is too short" because the password "abc123" has less than 8 characters.

Swift

enum PasswordError: Error {
    case tooShort
}

func checkPassword(_ password: String) throws {
    if password.count < 8 {
        throw PasswordError.tooShort
    }
}

do {
    try checkPassword("abc123")
    print("Password is strong enough")
} catch PasswordError.tooShort {
    print("Password is too short")
}

# Run the program to see the output

Need a hint?

Run the code and check the console output.