Extension functions in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define an extension function isEven for Int that returns true if the number is even.

Android Kotlin

fun Int.[1](): Boolean = this % 2 == 0

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AisEven

BevenCheck

CcheckEven

DisOdd

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function name that does not describe the purpose clearly.

Forgetting to declare the function as an extension on Int.

The extension function name should be isEven to clearly indicate it checks if the number is even.

2fill in blank

medium

Complete the code to call the extension function isEven on the integer number.

Android Kotlin

val number = 10
val result = number.[1]()

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AcheckEven

BisEven

CisOdd

DevenCheck

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to call the function without parentheses.

Using a wrong function name.

You call the extension function by using the dot notation on the variable: number.isEven().

3fill in blank

hard

Fix the error in the extension function that tries to add a greet function to String but is missing the receiver type.

Android Kotlin

fun [1].greet() = "Hello, $this!"

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AString

Bthis

Cfun

Dgreet

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the receiver type causes a syntax error.

Placing the receiver type after the function name.

Extension functions must specify the receiver type before the function name, like fun String.greet().

4fill in blank

hard

Fill both blanks to create an extension function repeatText for String that repeats the string n times.

Android Kotlin

fun String.[1](n: Int): String = this.[2](n)

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ArepeatText

B*

C+

Drepeat

Attempts:

3 left

💡 Hint

Common Mistakes

Using operators like * or + directly on strings without the repeat function.

Choosing a function name that does not match the task.

The function name is repeatText. To repeat a string in Kotlin, use the repeat(n) function, but since this is an extension, we call this.repeat(n).

5fill in blank

hard

Fill all three blanks to create an extension function toTitleCase for String that capitalizes the first letter and makes the rest lowercase.

Android Kotlin

fun String.[1](): String = this.substring(0,1).[2]() + this.substring(1).[3]()

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

AtoTitleCase

Buppercase

Ccapitalize

Dlowercase

Attempts:

3 left

💡 Hint

Common Mistakes

Using capitalize() which capitalizes the first letter but leaves the rest unchanged.

Not converting the rest of the string to lowercase.

The function name is toTitleCase. Use substring(0,1).uppercase() to capitalize the first character and lowercase() on the rest with substring(1).