Closures as function parameters in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to call the function with a closure that prints "Hello".

Swift

func greet(action: () -> Void) {
    action()
}

greet [1] {
    print("Hello")
}

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

A()

B(action: () -> Void)

C(action: () -> Void) -> Void

D() -> Void

Attempts:

3 left

💡 Hint

Common Mistakes

Including the closure type in the call instead of just parentheses.

Omitting parentheses entirely when no parameters are passed.

The function greet is called with a trailing closure, so just empty parentheses () are needed before the closure block.

2fill in blank

medium

Complete the function parameter to accept a closure that takes an Int and returns an Int.

Swift

func modify(number: Int, with closure: [1]) -> Int {
    return closure(number)
}

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

A() -> Int

B(Int) -> Int

C(Int) -> Void

D(Int, Int) -> Int

Attempts:

3 left

💡 Hint

Common Mistakes

Using a closure type that returns Void instead of Int.

Using a closure type with no parameters.

The closure parameter must take an Int and return an Int, so the type is (Int) -> Int.

3fill in blank

hard

Fix the error in the closure parameter type to accept a closure that takes two Ints and returns Bool.

Swift

func compare(a: Int, b: Int, using predicate: [1]) -> Bool {
    return predicate(a, b)
}

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A(Bool, Bool) -> Int

B(Int) -> Bool

C(Int, Int) -> Bool

D() -> Bool

Attempts:

3 left

💡 Hint

Common Mistakes

Using a closure type with only one parameter.

Using a closure type with wrong parameter or return types.

The closure must take two Int parameters and return a Bool, so the type is (Int, Int) -> Bool.

4fill in blank

hard

Fill both blanks to create a function that accepts a closure with no parameters and returns a String, then call it.

Swift

func fetchMessage(completion: [1]) {
    let message = completion()
    print(message)
}

fetchMessage [2] {
    return "Done"
}

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

A() -> String

B(String) -> Void

C()

D() -> Void

Attempts:

3 left

💡 Hint

Common Mistakes

Using closure types that return Void instead of String.

Omitting parentheses when calling the function.

The function parameter is a closure with no parameters returning String, so () -> String. The call uses empty parentheses () before the closure.

5fill in blank

hard

Complete the code to define and call a function that accepts a closure taking a String and returning an Int, then prints the result.

Swift

func process(text: String, with closure: [1]) {
    let length = closure(text)
    print("Length: \(length)")
}

process(text: "Swift") { text in
    return text.count
}

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

A(String) -> Int

B{

C}

Din

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting braces around the closure body.

Forgetting the 'in' keyword in the closure syntax.

The closure type is (String) -> Int. The closure syntax uses braces { } and the keyword in to separate parameters from the body.