Named companion objects in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a named companion object called Factory.

Kotlin

class MyClass {
    companion object [1] {
        fun create(): MyClass = MyClass()
    }
}

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

AFactory

BCompanion

CInstance

DObject

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving the companion object unnamed (empty).

Using keywords like 'Companion' as the name.

The named companion object is declared by giving a name after the companion object keyword. Here, Factory is the name.

2fill in blank

medium

Complete the code to call the create() function from the named companion object Factory.

Kotlin

val instance = MyClass.[1].create()

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ACompanion

BInstance

CObject

DFactory

Attempts:

3 left

💡 Hint

Common Mistakes

Using the default name 'Companion' instead of the given name.

Trying to call create() directly on the class without the companion object.

To access a named companion object, use the class name followed by the companion object's name. Here, Factory is the name.

3fill in blank

hard

Fix the error in the code by completing the companion object declaration with the correct name.

Kotlin

class User {
    companion object [1] {
        fun newUser() = User()
    }
}

val u = User.[1].newUser()

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ACreator

BCompanion

CFactory

DBuilder

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names in declaration and usage.

Using the default 'Companion' when the object is named differently.

The companion object must have the same name in both declaration and usage. Here, Factory is the correct name to fix the error.

4fill in blank

hard

Fill both blanks to create a named companion object called Helper and call its greet() function.

Kotlin

class Greeter {
    companion object [1] {
        fun greet() = "Hello"
    }
}

val message = Greeter.[2].greet()

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AHelper

BCompanion

CFactory

DAssistant

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names in declaration and call.

Using the default 'Companion' instead of the given name.

The companion object is named Helper and accessed by the same name to call greet().

5fill in blank

hard

Fill all three blanks to define a named companion object Creator with a function build(), then call it.

Kotlin

class Product {
    companion object [1] {
        fun build() = Product()
    }
}

val p = Product.[2].[3]()

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

ACreator

Bbuild

CFactory

DCompanion

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the companion object name and function name.

Using the default 'Companion' when the object is named differently.

The companion object is named Creator. The function build() is called from it.