Extensions for DSL building in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define an extension function named greet for the String class that prints a greeting message.

Kotlin

fun String.[1]() {
    println("Hello, $this!")
}

"World".greet()

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

Awelcome

Bhello

CsayHello

Dgreet

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name than the one called on the string.

Forgetting to define the function as an extension (missing 'String.' before the function name).

The extension function is named 'greet', so the blank should be filled with 'greet'.

2fill in blank

medium

Complete the code to create a DSL builder function html that takes a lambda with receiver of type HtmlBuilder.

Kotlin

fun html(block: [1].() -> Unit) {
    val builder = HtmlBuilder()
    builder.block()
    println(builder.result)
}

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

AHtmlBuilder

BString

CInt

DUnit

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong receiver type like String or Int.

Not matching the receiver type with the builder instance.

The lambda with receiver should be of type HtmlBuilder to allow building HTML inside the block.

3fill in blank

hard

Fix the error in the extension function that adds an li element inside a ul builder.

Kotlin

class UlBuilder {
    val items = mutableListOf<String>()
    fun li(text: String) {
        items.add(text)
    }
}

fun UlBuilder.[1](text: String) {
    li(text)
}

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

Ali

BlistItem

Citem

DaddItem

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name that does not match the existing method.

Causing ambiguity by defining a different name for the same action.

The extension function should have the same name 'li' to correctly add list items inside UlBuilder.

4fill in blank

hard

Fill both blanks to create a DSL function body inside HtmlBuilder that takes a lambda with receiver BodyBuilder.

Kotlin

class HtmlBuilder {
    var result = ""
    fun [1](block: [2].() -> Unit) {
        val bodyBuilder = BodyBuilder()
        bodyBuilder.block()
        result += bodyBuilder.content
    }
}

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

Abody

Bhead

CBodyBuilder

DHeadBuilder

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'head' or 'HeadBuilder' instead of 'body' and 'BodyBuilder'.

Mixing function name and receiver type.

The function name is 'body' and the lambda receiver type is 'BodyBuilder' to build the body content.

5fill in blank

hard

Fill all three blanks to create a DSL function div inside BodyBuilder that takes a lambda with receiver DivBuilder and appends the result.

Kotlin

class BodyBuilder {
    var content = ""
    fun [1](block: [2].() -> Unit) {
        val divBuilder = [3]()
        divBuilder.block()
        content += divBuilder.html
    }
}

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

Adiv

BDivBuilder

DBodyBuilder

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for function, receiver, or instance.

Confusing BodyBuilder with DivBuilder.

The function name is 'div', the lambda receiver is 'DivBuilder', and the instance created is 'DivBuilder()'.