Hi, I am investigating Kotlin Flows (On Android wi...

# coroutines

[Tower Guidev2]

Hi, I am investigating Kotlin Flows (On Android with Room/Sqlite DB)

[Tower Guidev2]

I have a requirement where I need to consume a Flow Once then "disable" it.

I have a Room database table where I have status values per "Action".
The status can be SUCCESS, EMPTY, FAILURE
each status row has an ARCHIVED column that is either true or false.

The DB table resembles this

data class OutcomeDO(
    @ColumnInfo(name = "name") val name: String,
    @ColumnInfo(name = "outcome") val outcome: Outcome,
    @ColumnInfo(name = "archived") val archived: Boolean = false,
) {
    @PrimaryKey(autoGenerate = true)
    @ColumnInfo(name = "result_local_id")
    var resultLocalId: Long = 0L
}

My DAO resembles this

@Query("SELECT * from result_table WHERE name = :name AND archived = :archive")
fun fetch(name: String, archive : Boolean = false): Flow<OutcomeDO>

I query this table like this:-

return database.outcomeDAO().fetch(name = Fred::class.java.name).filterNotNull().flatMapLatest { flowOf(it.outcome) }

and consume the Flow like this:-

outcome.take(1).collect { outcome ->
    when (outcome) {
        Success -> // display data
        Empty -> {
            showError(anchorView, R.string.no_data_found)
        }
        Failure -> {
            showError(anchorView, R.string.data_search_failed)
        }
    }
}

Once the flow has been consumed in the above snippet I wish to set that particular row on the underlying database to ARCHIVED = true

How can I achieve this?

Is there a Flow operator such as OnCompletion/OnConsumed that I can employ to detect when the flow has been consumed and allow me to update a specific row on my DB table?

[Tower Guidev2]

or how can I tell when a Flow has already been collected?

[Joffrey]

There is indeed onCompletion that you can add when you create the flow to detect the end of the collection (normally or exceptionally)