Functions and closures in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a simple function that prints a greeting.

iOS Swift

func greet() {
  print([1])
}

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

A"Hello, world!"

BHello, world!

Cprint("Hello")

Dgreet()

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the double quotes around the string.

Trying to call print inside print.

The print function requires a string argument enclosed in double quotes to print text.

2fill in blank

medium

Complete the code to declare a closure that adds two integers.

iOS Swift

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

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

A{ a, b in a - b }

B(a, b) -> a + b

Cfunc(a, b) { a + b }

D{ (a: Int, b: Int) in return a + b }

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect closure syntax without 'in'.

Using subtraction instead of addition.

A closure in Swift is defined with curly braces, parameters, 'in', and a return expression.

3fill in blank

hard

Fix the error in the function that returns a closure capturing a variable.

iOS Swift

func makeIncrementer() -> () -> Int {
  var count = 0
  return [1] {
    count += 1
    return count
  }
}

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

Aclosure()

Bfunc()

C{

D-> Int in

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'func()' instead of '{' to start the closure.

Adding extra keywords inside the return statement.

The closure should start with an opening brace '{' without extra keywords.

4fill in blank

hard

Fill both blanks to create a closure that filters even numbers from an array.

iOS Swift

let numbers = [1, 2, 3, 4, 5]
let evens = numbers.filter { [1] in [2] % 2 == 0 }

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

Anumber

Bnum

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names before 'in' and inside the closure.

Using undefined variable names.

The closure parameter name must be consistent; here 'number' is used both times.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension filtering values greater than zero.

iOS Swift

let data = ["a": 1, "b": -1, "c": 3]
let filtered = data.filter { [1], [2] in [3] > 0 }

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

Akey

Bvalue

Cval

Dk

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent parameter names.

Checking the key instead of the value.

The closure parameters are key and value; here 'k' and 'value' are used, and 'value' is checked.