Trailing closure syntax in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to call the function with a trailing closure.

Swift

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

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

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

A() -> Void

B()()

C()

D(action:)

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the parentheses when the function requires them.

Trying to put the closure inside the parentheses.

The function greet is called with an empty parameter list followed by a trailing closure in braces.

2fill in blank

medium

Complete the code to use trailing closure syntax with a function that takes one closure parameter.

Swift

func perform(task: () -> Void) {
    task()
}

perform[1] {
    print("Task done")
}

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

A()

B(task:)

C() -> Void

D(task)

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to name the closure parameter in the call.

Omitting the parentheses entirely.

The function perform is called with empty parentheses followed by the trailing closure.

3fill in blank

hard

Fix the error in the function call using trailing closure syntax.

Swift

func calculate(operation: (Int, Int) -> Int) -> Int {
    return operation(3, 4)
}

let result = calculate [1] (3, 4) in
    $0 + $1

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

A<

B(

C[

D{

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses instead of braces for the closure.

Trying to put closure parameters inside the parentheses.

Trailing closures use braces { } after the function call parentheses, not parentheses or other brackets.

4fill in blank

hard

Complete the code to correctly use trailing closure syntax with a function that has two parameters, the second is a closure.

Swift

func fetchData(from url: String, completion: (String) -> Void) {
    completion("Data from \(url)")
}

fetchData(from: {BLANK_1}}) { data in
    print(data)

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

A"https://api.example.com"

B{

C(

D"example.com"

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses instead of braces for the closure.

Passing the URL outside the parentheses.

The URL string is passed as the first argument inside parentheses, then the trailing closure starts with a brace.

5fill in blank

hard

Complete the code to create a dictionary using trailing closure syntax with mapValues.

Swift

let numbers = ["one": 1, "two": 2, "three": 3]

let strings = numbers.mapValues { number in
    String(number) + [1] "!" + }

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

A{

B"!"

C"?"

D}

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses instead of braces for the closure.

Using wrong string literals or missing the closing brace.

The closure starts with {, concatenates the string "!", and ends with }.