Room with Flow for reactive data in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a Flow that observes all users from the DAO.

Android Kotlin

fun getAllUsers(): [1]<List<User>>

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

AFlow

BObservable

CList

DLiveData

Attempts:

3 left

💡 Hint

Common Mistakes

Using LiveData instead of Flow when Flow is required.

Returning a plain List instead of a reactive stream.

Room supports Flow to provide reactive streams of data.

2fill in blank

medium

Complete the code to collect data from the Flow in a coroutine scope.

Android Kotlin

lifecycleScope.launch {
  userDao.getAllUsers().[1] { users ->
    // update UI with users
  }
}

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

Aobserve

Bsubscribe

Ccollect

Dlaunch

Attempts:

3 left

💡 Hint

Common Mistakes

Using observe which is for LiveData, not Flow.

Trying to subscribe like RxJava instead of collect.

To get data from a Flow, you collect it inside a coroutine.

3fill in blank

hard

Fix the error in the DAO function to return a Flow of users.

Android Kotlin

@Query("SELECT * FROM users")
fun getUsers(): [1]<List<User>>

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AList

BLiveData

CObservable

DFlow

Attempts:

3 left

💡 Hint

Common Mistakes

Returning List directly which is not reactive.

Using LiveData instead of Flow in Kotlin coroutines.

The DAO must return a Flow to enable reactive updates.

4fill in blank

hard

Fill both blanks to create a Flow that filters users older than 18.

Android Kotlin

fun getAdultUsers(): [1]<List<User>> = userDao.getAllUsers()
  .[2] { list -> list.filter { it.age > 18 } }

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

AFlow

Bmap

Cfilter

DLiveData

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter on Flow which filters emissions, not list items.

Returning LiveData instead of Flow.

Use Flow as return type and map to transform the emitted list.

5fill in blank

hard

Fill the blanks to debounce rapid Flow emissions and collect them.

Android Kotlin

lifecycleScope.launch {
  userDao.getAllUsers()
    .[1](300)
    .[2] { users ->
      // update UI
    }
}

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

Adebounce

BcollectLatest

Ccollect

Dmap

Attempts:

3 left

💡 Hint

Common Mistakes

Using collect without debounce causing too many updates.

Using map instead of debounce for timing control.

Use debounce to wait for 300ms of silence, collectLatest to cancel previous work.