Why functions are first-class in Swift - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a function variable that adds two numbers.

Swift

let add: (Int, Int) -> Int = [1]

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

Aadd(a: Int, b: Int) -> Int { a + b }

Bfunc add(a: Int, b: Int) -> Int { return a + b }

C{ (a, b) in a + b }

D(a, b) -> a + b

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to assign a function declaration instead of a closure.

Missing the 'in' keyword in the closure.

In Swift, you can assign a closure to a variable. The correct syntax for a closure that adds two numbers is { (a, b) in a + b }.

2fill in blank

medium

Complete the code to call the function stored in the variable.

Swift

let result = add[1]3, 5)

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

A<

B[

C{

D(

Attempts:

3 left

💡 Hint

Common Mistakes

Using square brackets or braces instead of parentheses.

Forgetting to include the opening parenthesis.

To call a function or closure in Swift, use parentheses with arguments inside, like add(3, 5).

3fill in blank

hard

Fix the error in the function assignment by choosing the correct syntax.

Swift

let multiply: (Int, Int) -> Int = [1](a, b) in { return a * b }

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

A{

Bfunc

Clet

Dvar

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'func' keyword inside a closure assignment.

Not using curly braces for closures.

When assigning a closure to a variable, use curly braces {} around the closure body, not the func keyword.

4fill in blank

hard

Fill both blanks to create a function that takes another function as a parameter and calls it.

Swift

func performOperation(_ operation: (Int, Int) -> Int, _ a: Int, _ b: Int) -> Int {
    return operation[1]a, b[2]
}

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

A(

B)

C[

D]

Attempts:

3 left

💡 Hint

Common Mistakes

Using square brackets instead of parentheses.

Forgetting to close the parentheses.

To call the function parameter operation, use parentheses around the arguments: operation(a, b).

5fill in blank

hard

Fill all three blanks to create a dictionary that maps strings to functions and call one of them.

Swift

let operations: [String: (Int, Int) -> Int] = [
    "add": [1],
    "subtract": [2]
]

let result = operations["add"][3](10, 5)!

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

A{ (a, b) in a + b }

B{ (a, b) in a - b }

C?

D!

Attempts:

3 left

💡 Hint

Common Mistakes

Using '?' instead of '!' to unwrap the optional.

Not using closures as dictionary values.

The dictionary stores closures for addition and subtraction. To call a function from the dictionary safely, use the forced unwrap operator ! after the call, since the dictionary returns an optional.