Inner class access to outer members in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to access the outer class property from the inner class.

Kotlin

class Outer {
    val greeting = "Hello"
    inner class Inner {
        val greeting = "inner"
        fun greet() = [1]
    }
}

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

[e-mail]

Bthis.greeting

COuter.greeting

Dgreeting

Attempts:

3 left

💡 Hint

Common Mistakes

Using just 'greeting' or 'this.greeting' accesses inner class scope, not outer.

In Kotlin, to access an outer class member from an inner class, use this@Outer.

2fill in blank

medium

Complete the code to call the outer class function from the inner class.

Kotlin

class Outer {
    fun outerFun() = "Outer Function"
    inner class Inner {
        fun outerFun() = "inner"
        fun callOuter() = [1]
    }
}

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AouterFun()

Bthis.outerFun()

[e-mail]()

DOuter.outerFun()

Attempts:

3 left

💡 Hint

Common Mistakes

Calling outerFun() directly calls the inner class function.

Use [e-mail]() to call the outer class function from the inner class.

3fill in blank

hard

Fix the error in accessing the outer property inside the inner class method.

Kotlin

class Outer {
    val number = 42
    inner class Inner {
        val number = 0
        fun printNumber() {
            println([1])
        }
    }
}

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Anumber

[e-mail]

Cthis.number

DOuter.number

Attempts:

3 left

💡 Hint

Common Mistakes

Using number or this.number accesses the inner class property.

Use [e-mail] to correctly access the outer class property.

4fill in blank

hard

Fill both blanks to access outer class property and call its function from inner class.

Kotlin

class Outer {
    val text = "Hi"
    fun outerFun() = "Called"
    inner class Inner {
        val text = "inner"
        fun outerFun() = "inner func"
        fun combined() = [1] + " " + [2]()
    }
}

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[e-mail]

Btext

[e-mail]

DouterFun

Attempts:

3 left

💡 Hint

Common Mistakes

Using unqualified names causes errors or accesses inner class members.

Use [e-mail] to access the property and [e-mail]() to call the function.

5fill in blank

hard

Fill all three blanks to create a map with outer property keys and inner class method results as values.

Kotlin

class Outer {
    val prefix = "Key"
    inner class Inner {
        fun suffix() = "Value"
        fun createMap() = mapOf([1] to [2].[3]())
    }
}

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Aprefix

Bthis@Outer

Cthis

Dsuffix

Attempts:

3 left

💡 Hint

Common Mistakes

Using this@Outer to call inner methods causes errors.

The map key is the outer property prefix. The value calls the inner class method suffix() using this.suffix().