Kotlin Kotlin Extensions and Delegates 3

Question 1

How do you check if a `lateinit var` has been initialized in Kotlin?

Accepted Answer

Using `::property.isInitialized`

Answer

The `::property.isInitialized` reflection check lets you safely verify whether a `lateinit var` has been assigned before accessing it.

Question 2

What is a receiver in the context of Kotlin extension functions?

Accepted Answer

The object on which the extension function is called, accessible as `this`

Answer

The receiver is the instance on which an extension function is invoked; inside the extension, it can be accessed implicitly as `this`.

Question 3

Can extension functions be defined on nullable types in Kotlin?

Accepted Answer

Yes, using `fun Type?.functionName()` syntax

Answer

Kotlin allows extension functions on nullable types by adding `?` to the receiver type, enabling safe calls without null checks at the call site.

Question 4

What is a DSL in Kotlin and how are extension functions used to build them?

Accepted Answer

A Domain-Specific Language built using extension functions and lambdas with receivers for readable configuration code

Answer

Kotlin DSLs use extension functions, lambdas with receivers, and infix functions to create readable, type-safe configuration APIs like Gradle Kotlin DSL or HTML builders.

Question 5

What is a lambda with receiver in Kotlin?

Accepted Answer

A lambda where `this` is bound to the specified receiver type, enabling DSL-like code

Answer

A lambda with receiver (e.g., `String.() -> Unit`) is called with `this` bound to the receiver object, allowing direct member access without qualification.

Kotlin Practice Test

Kotlin Practice Test

Kotlin Kotlin Extensions and Delegates 3