CompactMap for optional unwrapping in Swift - Mini Project: Build & Apply

CompactMap for optional unwrapping

📖 Scenario: You have a list of strings representing ages of people. Some strings are valid numbers, and some are not. You want to get a list of only the valid ages as integers.

🎯 Goal: Build a Swift program that uses compactMap to convert an array of optional strings into an array of non-optional integers, filtering out invalid entries.

📋 What You'll Learn

Create an array of strings called ageStrings with the exact values: ["25", "thirty", "42", "", "18"]

Create a variable called validAges that uses compactMap on ageStrings to convert strings to Int

Print the validAges array

💡 Why This Matters

🌍 Real World

Filtering and converting user input or data from text sources where some values may be invalid or missing.

💼 Career

Data cleaning and transformation is a common task in app development, especially when handling user input or external data.

1

Create the array of age strings

Create an array called ageStrings with these exact string values: ["25", "thirty", "42", "", "18"]

Swift

# Create the array ageStrings with the given values
# Your code here

Need a hint?

Use square brackets to create an array of strings.

2

Use compactMap to convert strings to integers

Create a variable called validAges that uses compactMap on ageStrings to convert each string to an Int.

Swift

let ageStrings = ["25", "thirty", "42", "", "18"]
# Use compactMap on ageStrings to create validAges
# Your code here

Need a hint?

Use compactMap with a closure that tries to convert each string to Int.

3

Print the valid ages

Write a print statement to display the validAges array.

Swift

let ageStrings = ["25", "thirty", "42", "", "18"]
let validAges = ageStrings.compactMap { Int($0) }
# Print the validAges array
# Your code here

Need a hint?

Use print(validAges) to show the result.

4

Run and check the output

Run the program and observe the output. It should print the array of valid ages as integers.

Swift

let ageStrings = ["25", "thirty", "42", "", "18"]
let validAges = ageStrings.compactMap { Int($0) }
print(validAges)
# Run the program to see the output

Need a hint?

The output should be [25, 42, 18] because only these strings convert to integers.