Kotlin Kotlin Extensions and Delegates 2

Question 1

What is property delegation in Kotlin?

Accepted Answer

Delegating the implementation of a property's get/set to another object

Answer

Property delegation lets you hand off the `get` and `set` implementations to a delegate object, enabling reusable property behavior.

Question 2

What does `Delegates.notNull()` do in Kotlin?

Accepted Answer

Ensures a property is initialized before access, throwing if accessed before assignment

Answer

`Delegates.notNull()` creates a property that throws an `IllegalStateException` if read before being assigned a value.

Question 3

What is `lateinit` used for in Kotlin?

Accepted Answer

Allowing non-nullable var properties to be initialized after declaration without using null

Answer

`lateinit` allows non-nullable `var` properties to be declared without immediate initialization, useful for dependency injection and unit tests.

Question 4

What is the difference between `lazy` and `lateinit` in Kotlin?

Accepted Answer

`lazy` is for val properties with computed initialization; `lateinit` is for var properties initialized externally

Answer

`lazy` is used with `val` and initializes via a lambda on first access, while `lateinit` is for `var` properties that will be set later by external code.

Question 5

Which scope function is best for configuring a newly created object?

Accepted Answer

apply

Answer

`apply` calls a block with the object as `this`, allows you to configure it in place, and returns the object — perfect for builder-style setup.

Kotlin Practice Test

Kotlin Practice Test

Kotlin Kotlin Extensions and Delegates 2