WithContext for dispatcher switching in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to switch to the IO dispatcher using withContext.

Kotlin

suspend fun fetchData() {
    withContext([1]) {
        // perform IO operation
    }
}

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

ADispatchers.Main

BDispatchers.Default

CDispatchers.IO

DDispatchers.Unconfined

Attempts:

3 left

💡 Hint

Common Mistakes

Using Dispatchers.Main for IO tasks causes blocking on the main thread.

Using Dispatchers.Default is for CPU-intensive tasks, not IO.

The Dispatchers.IO is used for IO-bound tasks like reading from disk or network calls.

2fill in blank

medium

Complete the code to switch to the Default dispatcher inside withContext.

Kotlin

suspend fun calculate() {
    withContext([1]) {
        // CPU-intensive calculation
    }
}

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

ADispatchers.Main

BDispatchers.Default

CDispatchers.IO

DDispatchers.Unconfined

Attempts:

3 left

💡 Hint

Common Mistakes

Using Dispatchers.IO for CPU tasks can cause thread starvation.

Using Dispatchers.Main blocks the UI thread.

Dispatchers.Default is used for CPU-intensive tasks like calculations.

3fill in blank

hard

Fix the error in the code by choosing the correct dispatcher for UI updates.

Kotlin

suspend fun updateUI() {
    withContext([1]) {
        // update UI elements
    }
}

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

ADispatchers.Main

BDispatchers.Unconfined

CDispatchers.IO

DDispatchers.Default

Attempts:

3 left

💡 Hint

Common Mistakes

Using Dispatchers.IO causes UI update crashes.

Using Dispatchers.Default runs UI code off the main thread.

UI updates must happen on the Dispatchers.Main to avoid threading issues.

4fill in blank

hard

Fill both blanks to create a map of words to their lengths, filtering words longer than 4 characters.

Kotlin

val words = listOf("apple", "cat", "banana", "dog")
val lengths = words.associateWith { [1] }
    .filter { it.value [2] 4 }

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Ait.length

B>

C<

Dit.count()

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of > filters shorter words.

Using it.count() is valid but less common than it.length.

it.length gets the length of each word, and filtering with > 4 keeps words longer than 4 characters.

5fill in blank

hard

Fill all three blanks to create a map of uppercase words to their lengths, filtering lengths greater than 3.

Kotlin

val words = listOf("one", "two", "three", "four")
val result = words.associateBy([1]) { [2] }
    .filter { it.value [3] 3 }

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Ait.uppercase()

Bit.length

C>

Dit.lowercase()

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase keys instead of uppercase.

Filtering with < instead of >.

We use it.uppercase() as the key, it.length as the value, and filter values greater than 3.