Map-backed delegated properties in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a map-backed delegated property for 'name'.

Kotlin

val user = mapOf("name" to "Alice", "age" to 30)
val name: String by [1]

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

Amap

Buser

CmutableMapOf()

DHashMap()

Attempts:

3 left

💡 Hint

Common Mistakes

Using a new empty map instead of the existing 'user' map.

The property 'name' is delegated to the map 'user'. This means 'name' will get its value from the map's 'name' key.

2fill in blank

medium

Complete the code to access the 'age' property delegated to the map.

Kotlin

val user = mapOf("name" to "Bob", "age" to 25)
val age: Int by [1]
println(age)

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

Amap

BmutableMapOf()

CHashMap()

Duser

Attempts:

3 left

💡 Hint

Common Mistakes

Delegating to a new empty map which has no data.

The 'age' property is delegated to the 'user' map, so it retrieves the value associated with the 'age' key.

3fill in blank

hard

Fix the error in the code to correctly delegate 'email' property to the map.

Kotlin

val user = mapOf("email" to "[e-mail]")
val email: String by [1]
println(email)

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

Amap

BmutableMapOf()

Cuser

DHashMap()

Attempts:

3 left

💡 Hint

Common Mistakes

Delegating to a new empty map instead of the existing one.

The property 'email' must delegate to the existing 'user' map to access the stored value.

4fill in blank

hard

Fill both blanks to create a map-backed delegated property 'city' and print its value.

Kotlin

val data = mapOf("city" to "Paris", "country" to "France")
val city: String by [1]
println([2])

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

Adata

Bcity

Ccountry

DdataMap

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names for delegation or printing.

The property 'city' delegates to the map 'data'. To print the value, use the property name 'city'.

5fill in blank

hard

Fill all three blanks to create map-backed delegated properties 'firstName' and 'lastName', then print full name.

Kotlin

val personData = mapOf("firstName" to "John", "lastName" to "Doe")
val firstName: String by [1]
val lastName: String by [2]
println("Full name: $[3] $lastName")

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

ApersonData

CfirstName

DlastName

Attempts:

3 left

💡 Hint

Common Mistakes

Using different map variables for delegation or printing the map variable instead of the property.

Both 'firstName' and 'lastName' delegate to the 'personData' map. To print the full name, use the 'firstName' property followed by 'lastName'.