Apply function behavior and use cases in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to use the apply function to initialize the object.

Kotlin

val person = Person().[1] {
    name = "Alice"
    age = 30
}

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

Aapply

Balso

Crun

Dlet

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'let' instead of 'apply' which returns the last expression, not the object.

Using 'run' which returns the lambda result, not the object.

Using 'also' which uses 'it' as context, not 'this'.

The apply function allows you to configure an object within its scope and returns the object itself.

2fill in blank

medium

Complete the code to print the object's properties using apply.

Kotlin

val car = Car().[1] {
    brand = "Toyota"
    year = 2020
    println("Brand: $brand, Year: $year")
}

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

Aapply

Bwith

Calso

Dlet

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'also' which uses 'it' and is less convenient for property access.

Using 'let' which returns the lambda result, not the object.

Using 'with' which is not called as an extension function.

apply lets you configure the object and run code inside its scope using this. Here, it prints properties after setting them.

3fill in blank

hard

Fix the error in the code by choosing the correct function to initialize and return the object.

Kotlin

val book = Book().[1] {
    title = "Kotlin Guide"
    pages = 250
}
println(book.title)

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

Alet

Bapply

Crun

Dalso

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'let' or 'run' which return the lambda result, not the object.

Using 'also' which uses 'it' and is less convenient here.

apply returns the object after applying changes, so book holds the initialized object.

4fill in blank

hard

Fill both blanks to create a mutable list and add elements using apply.

Kotlin

val numbers = mutableListOf<Int>()[1] {
    add(1)
    add(2)
    add(3)
}[2]
println(numbers)

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

Aapply

Blet

Calso

Drun

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'let' or 'run' which return the lambda result, not the list.

Using 'also' which uses 'it' and is less convenient for adding elements.

Using apply both times lets you add elements inside the block and returns the list itself for printing.

5fill in blank

hard

Fill all three blanks to create a data class instance, configure it with apply, and print its properties.

Kotlin

data class User(var username: String = "", var email: String = "")

val user = User()[1] {
    username = "john_doe"
    email = "[e-mail]"
}

println("Username: ${user.[2], Email: ${user.[3]")

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

Aapply

Busername

Cemail

Dlet

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'let' instead of 'apply' which returns the lambda result.

Misspelling property names in the print statement.

Using 'also' which uses 'it' and is less convenient here.

apply is used to configure the User object. Then, the properties username and email are accessed to print their values.