Defer statement for cleanup in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print "Cleanup done" after the function finishes.

Swift

func example() {
    [1] {
        print("Cleanup done")
    }
    print("Function running")
}

Drag options to blanks, or click blank then click option'

Aguard

Bwhile

Cif

Ddefer

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'if' or 'while' instead of 'defer' does not delay execution until function end.

The defer statement schedules code to run just before the function returns, perfect for cleanup.

2fill in blank

medium

Complete the code to ensure the file is closed after reading.

Swift

func readFile() {
    let file = openFile()
    [1] {
        file.close()
    }
    print("Reading file")
}

Drag options to blanks, or click blank then click option'

Aguard

Brepeat

Cdefer

Dswitch

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'guard' or 'switch' does not guarantee cleanup after function ends.

The defer statement ensures file.close() runs when the function ends, even if errors occur.

3fill in blank

hard

Fix the error by completing the code to defer the cleanup print statement.

Swift

func process() {
    [1] {
        print("Cleanup after processing")
    }
    print("Processing data")
}

Drag options to blanks, or click blank then click option'

Aif

Bdefer

Cguard

Drepeat

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'if' or 'guard' does not delay execution to the end of the function.

Only defer correctly delays the cleanup print until the function ends.

4fill in blank

hard

Fill both blanks to defer two cleanup print statements in order.

Swift

func cleanup() {
    [1] {
        print("First cleanup")
    }
    [2] {
        print("Second cleanup")
    }
    print("Function body")
}

Drag options to blanks, or click blank then click option'

Adefer

Bguard

Cif

Drepeat

Attempts:

3 left

💡 Hint

Common Mistakes

Using different keywords for the two blocks breaks the defer behavior.

Using defer twice schedules both cleanup prints to run in reverse order after the function ends.

5fill in blank

hard

Fill all three blanks to defer cleanup and print variable values correctly.

Swift

func example() {
    let x = 10
    [1] {
        print("Cleanup x: \(x)")
    }
    let y = 20
    [2] {
        print("Cleanup y: \(y)")
    }
    print("Values: \(x), \(y)")
    [3] {
        print("Final cleanup")
    }
}

Drag options to blanks, or click blank then click option'

Adefer

Bguard

Cif

Drepeat

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'guard' or 'if' instead of 'defer' breaks the cleanup scheduling.

All three defer statements schedule cleanup prints to run in reverse order after the function ends.