Properties

Question 1

If you need to change the visibility of an accessor or to annotate it, but don’t need to change the ___ ___, you can define the accessor without defining it’s ___.

Answer 1

default implementation; body

Question 2

When a property needs a ___ ___, Kotlin provides it automatically.

Answer 2

backing field

Question 3

The ‘field’ identifier can only be used in the ___ of the property.

Answer 3

accessors

Question 4

A backing field will be generated for a property if it uses the ___ ___ of at least one of the accessors, or if a custom accessor references it through the ___ identifier.

Answer 4

default implementation; field

Question 5

If the value of a read-only property is known at compile time, mark it as a compile time constant using the ___ qualifier.

Answer 5

const

Question 6

Compile time constants must fulfil the following requirements:

Answer 6

Top-level, or member of an object declaration or a companion object; Initialized with a value of type ‘String’ or a primitive type; No custom getter

Question 7

True or False: Compile time constants can be used in annotations.

Answer 7

true

Question 8

The ‘lateinit var’ modifier may not be used on:

Answer 8

nullable types; primitive types

Question 9

To check whether a ‘lateinit var’ has already been initialized, use the ___ property.

Answer 9

isInitialized

Question 10

The expression after ‘by’ is the ___, because ‘get()’ and ‘set()’ corresponding to the property will be delegated to its ___ and ___ methods.

Answer 10

delegate; getValue(); setValue()

Question 11

‘lazy()’ is a function that takes a lambda and returns an instance of ‘Lazy’ which can serve as a ___ for implementing a ___ ___.

Answer 11

delegate; lazy property

Question 12

By default, the evaluation of lazy properties is ___.

Answer 12

synchronized

Question 13

If the synchronization of initialization of a delegate is not required, so that multiple threads can execute it simultaneously, pass ___ as a parameter to the ___ function.

Answer 13

LazyThreadSafetyMode.PUBLICATION; lazy()

Question 14

If you’re sure that the initialization will always happen on the same thread as the one where you use the property, you can use ___.

Answer 14

LazyThreadSafetyMode.NONE

Question 15

‘Delegates.observable()’ takes two arguments: the ___ ___ and a ___ for modifications.

Answer 15

initial value; handler

Question 16

If you want to intercept assignments and “veto” them, use ___ instead of ‘observable()’.

Answer 16

vetoable()

Question 17

The handle for ‘Delegates.observable()’ is called ___ the assignment has been performed.

Answer 17

after

Question 18

The handler passed to ‘vetoable’ is called ___ the assignment of a new property as been performed.

Answer 18

before

Question 19

A property can delegate its getter and setter to another ___.

Answer 19

property

Question 20

Delegation to another property is available for both ___ and ___ properties. (member and extension)

Answer 20

top-level; class

Question 21

What 3 things must a delegate property be?

Answer 21

a top-level property; a member or an extension property of the same class; a member or an extension property of another class

Question 22

To delegate a property to another property, use the ___ qualifier in the delegate name.

Answer 22

:: (double colon)

Question 23

What is one use case for delegating a property to another property?

Answer 23

renaming a property in a backwards compatible way

Question 24

How would you use a map instance as the delegate for a delegated property?

Answer 24

Question 25

Using a map as a delegate for properties also works for ___ properties if you use a ___ instead of a read-only ___.

Answer 25

‘var’; MutableMap; Map

Question 26

You can declare ___ variables as delegated properties.

Answer 26

local

Question 27

For a read-only property (val), a delegate has to provide an operator function ‘getValue()’ with the following parameters:

Answer 27

Question 28

For a mutable property (var), a delegate has to additionally provide an operator function ‘setValue()’ with the following parameters:

Answer 28

Question 29

‘getValue()’ and/or ‘setValue()’ functions may be provided either as member functions of the delegate class or ___ ___.

Answer 29

extension functions

Question 30

You can create delegates as ___ objects without creating new classes using the interfaces ___ and ___ from the Kotlin standard library.

Answer 30

anonymous; ReadOnlyProperty; ReadWriteProperty