Functions and lambdas in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a function named greet that takes no parameters and returns a String.

Android Kotlin

fun greet(): [1] {
  return "Hello!"
}

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

ABoolean

BInt

CUnit

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using Unit as return type when function returns a value.

Using Int or Boolean instead of String.

The function greet returns a String, so the return type must be String.

2fill in blank

medium

Complete the code to define a lambda that takes two Ints and returns their sum.

Android Kotlin

val sum: (Int, Int) -> Int = [1]

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

A{ a, b -> a * b }

B(a, b) -> a - b

C{ a, b -> a + b }

D(a, b) -> a / b

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses instead of curly braces for lambda body.

Using subtraction or multiplication instead of addition.

The lambda syntax uses curly braces with parameters and an arrow, here adding a and b.

3fill in blank

hard

Fix the error in the function declaration to make it a valid Kotlin function that returns Unit.

Android Kotlin

fun printMessage(message: String)[1] {
  println(message)
}

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

A: Unit

B-> Unit

C-> String

D: String

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-> Unit' which is invalid syntax for function return type.

Using String as return type when function returns nothing.

In Kotlin, functions returning Unit use ': Unit' after the parameter list.

4fill in blank

hard

Fill both blanks to create a lambda that filters a list of Ints to only even numbers.

Android Kotlin

val evens = numbers.filter { [1] -> [2] % 2 == 0 }

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

Anum

Bnumber

Ditem

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for parameter and inside the lambda body.

Using invalid variable names.

The lambda parameter name must be consistent; here 'number' is used for both parameter and in the body.

5fill in blank

hard

Fill all three blanks to create a function that takes a lambda and calls it with 5.

Android Kotlin

fun callWithFive(action: (Int) -> Unit) {
  action([1])
}

callWithFive { [2] -> println([3]) }

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

A5

Bx

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Passing wrong value to the lambda.

Using different names for lambda parameter and inside body.

The function calls the lambda with 5; the lambda parameter is named x and printed.