Factory pattern with companion objects in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a companion object inside the class.

Kotlin

class Car {
    [1] object {
        fun create() = Car()
    }
}

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

Acompanion

BFactory

Cobject

DCompanion

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase 'Companion' instead of lowercase 'companion'.

Forgetting the keyword 'companion' before 'object'.

In Kotlin, the keyword companion is used to declare a companion object inside a class.

2fill in blank

medium

Complete the factory method to create a Car instance.

Kotlin

class Car {
    companion object {
        fun [1](): Car {
            return Car()
        }
    }
}

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

Acreate

Bnew

Cbuild

Dmake

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'new' which is not a function name in Kotlin.

Using unrelated method names like 'build' or 'make' without context.

The factory method is commonly named create to indicate it returns a new instance.

3fill in blank

hard

Fix the error in the factory method call to create a Car instance.

Kotlin

fun main() {
    val car = Car.[1]()
    println("Car created: $car")
}

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

AnewCar

Bcreate

Cbuild

Dmake

Attempts:

3 left

💡 Hint

Common Mistakes

Using method names that do not exist in the companion object.

Trying to call a constructor directly instead of using the factory method.

The correct factory method name is create as defined in the companion object.

4fill in blank

hard

Fill both blanks to complete the factory pattern with a companion object and a private constructor.

Kotlin

class Bike private constructor() {
    companion object {
        fun [1](): Bike {
            return Bike()
        }
    }
}

fun main() {
    val bike = Bike.[2]()
    println("Bike created: $bike")
}

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

Acreate

Bbuild

Cmake

Dnew

Attempts:

3 left

💡 Hint

Common Mistakes

Using different method names for declaration and call.

Trying to call the constructor directly which is private.

The factory method is named create and is called as Bike.create() to create a new instance.

5fill in blank

hard

Fill all three blanks to implement a factory pattern with companion object, private constructor, and a property.

Kotlin

class Truck private constructor(val model: String) {
    companion object {
        fun [1](model: String): Truck {
            return Truck([2])
        }
    }
}

fun main() {
    val truck = Truck.[3]("BigTruck")
    println("Truck model: ${truck.model}")
}

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

Acreate

Bmodel

C"model"

DmodelName

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the parameter as a string literal instead of the variable.

Using inconsistent method names for factory method declaration and call.

The factory method is named create. It takes a parameter model and passes it to the private constructor. The call uses Truck.create("BigTruck").