This vs it receiver difference in Kotlin - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print the name using 'this' receiver inside the class.

Kotlin

class Person(val name: String) {
    fun printName() {
        println([1].name)
    }
}

fun main() {
    val p = Person("Anna")
    p.printName()
}

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

Ait

Bthis

Cself

Dthat

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'it' instead of 'this' inside class methods.

In Kotlin, this refers to the current object instance inside a class.

2fill in blank

medium

Complete the lambda expression to print the name using the implicit 'it' receiver.

Kotlin

val names = listOf("Anna", "Bob")
names.forEach { [1] ->
    println([1])
}

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Aname

Bit

Cthis

Dself

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'it' when parameter is explicitly named.

In a lambda with explicit parameter, you name the parameter (here 'name') and use it inside.

3fill in blank

hard

Fix the error by choosing the correct receiver to access the property inside the lambda with receiver.

Kotlin

class Person(val name: String) {
    fun greet() {
        val printName = with(this) {
            {
                println([1].name)
            }
        }
        printName()
    }
}

fun main() {
    val p = Person("Anna")
    p.greet()
}

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Aself

Bit

Cthis

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'it' inside 'with' lambda which uses 'this' receiver.

Inside 'with(this)', 'this' refers to the Person object, so use 'this.name'.

4fill in blank

hard

Fill both blanks to correctly use 'this' and 'it' in nested lambdas.

Kotlin

class Person(val name: String) {
    fun greetAll(names: List<String>) {
        names.forEach [1] ->
            println("Hello, $[2]!")
    }
}

fun main() {
    val p = Person("Anna")
    p.greetAll(listOf("Bob", "Carol"))
}

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Aname

Bit

Cthis.name

Dself

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'this.name' inside the lambda instead of the parameter.

In forEach, the lambda parameter is 'it' by default, representing each name. Inside the string, we use 'name' from the lambda parameter.

5fill in blank

hard

Fill all three blanks to correctly use 'this' and 'it' in a nested scope with 'apply' and 'let'.

Kotlin

class Person(var greeting: String) {
    fun greet(name: String) {
        this.apply {
            greeting = "Hello"
            name.let [1] ->
                println("$[2], $[3]!")
        }
    }
}

fun main() {
    val p = Person("")
    p.greet("Bob")
}

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Ait

Bgreeting

Dthis.greeting

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing 'this' and 'it' inside nested lambdas.

Inside 'let', 'it' is the lambda parameter (the name). Inside 'apply', 'this' refers to the Person object, so use 'this.greeting'.