Kotlin Kotlin Extensions and Delegates

Question 1

What is an extension function in Kotlin?

Accepted Answer

A function added to an existing class without modifying its source code

Answer

Extension functions allow you to add new functions to existing classes without inheriting from them or using decorators.

Question 2

Can extension functions access private members of the extended class?

Accepted Answer

No, they can only access public and internal members

Answer

Extension functions do not have access to private or protected members of the class they extend; they can only use publicly visible APIs.

Question 3

What is an extension property in Kotlin?

Accepted Answer

A property added to an existing class without modifying its source

Answer

Extension properties add computed properties to existing classes without modifying them, but they cannot have backing fields.

Question 4

What does `by lazy` do in Kotlin?

Accepted Answer

Initializes a property lazily on first access using a lambda

Answer

`by lazy { }` creates a property that is computed only once on first access and cached for subsequent reads.

Question 5

Which standard delegate observable notifies you when a property value changes?

Accepted Answer

observable

Answer

`Delegates.observable` calls a handler function whenever the property value is changed, receiving the old and new values.

Kotlin Practice Test