Lambda with receiver concept in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a lambda with receiver that returns the length of the string.

Kotlin

val lengthLambda: String.() -> Int = { [1] }

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

Athis.length

Blength()

Clength

Dthis.length()

Attempts:

3 left

💡 Hint

Common Mistakes

Using length() which is not a function in Kotlin String.

Omitting this and just writing length which is not recognized.

In Kotlin, inside a lambda with receiver, this refers to the receiver object. To get the length of the string, use this.length.

2fill in blank

medium

Complete the code to call the lambda with receiver on the string "Hello".

Kotlin

val result = "Hello".[1](lengthLambda)

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

Awith

Blet

Crun

Dapply

Attempts:

3 left

💡 Hint

Common Mistakes

Using apply which returns the object, not the lambda result.

Using let which uses lambda with parameter, not receiver.

The run function calls the lambda with receiver on the object and returns the lambda result.

3fill in blank

hard

Fix the error in the lambda with receiver that tries to convert the string to uppercase.

Kotlin

val upperLambda: String.() -> String = { [1] }

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

Athis.toUpperCase()

BtoUpperCase()

CtoUpperCase

Dthis.toUpperCase

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting parentheses when calling toUpperCase.

Not using this which can cause confusion.

Inside the lambda with receiver, call the function with parentheses and use this to refer to the string.

4fill in blank

hard

Fill both blanks to create a lambda with receiver that repeats the string twice and checks if its length is greater than 5.

Kotlin

val checkLambda: String.() -> Boolean = { val repeated = this [1] 2; repeated.length [2] 5 }

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

A*

B+

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using * which is not valid for strings in Kotlin.

Using < instead of > for comparison.

Use + to repeat the string twice (concatenate it with itself), and > to check if length is greater than 5.

5fill in blank

hard

Fill all three blanks to create a map from strings to their uppercase versions only if the string length is less than 4.

Kotlin

val words = listOf("cat", "dog", "elephant")
val result = words.associateWith { it.[1]() }
    .filter { it.key.length [2] 4 }
    .mapValues { it.value.[3]() }

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

AtoUpperCase

B<

CtoLowerCase

Dlength

Attempts:

3 left

💡 Hint

Common Mistakes

Using length as a function call instead of property.

Mixing up toUpperCase and toLowerCase in wrong places.

First, convert each word to uppercase with toUpperCase(). Then filter words with length less than 4 using <. Finally, convert the values to lowercase with toLowerCase().