How to call a method on an element within a list that is contained in a Kotlin Flow

user_2395334 0
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I am wondering if there's a better way to call a method on an element within a list that is contained in a Flow. Currently i'm doing this but i don't like calling map() twice:

override fun getEarnings(): Flow<List<Transaction>> {
    return transactionDao.getEarnings().map {
        it.map { transaction -> transaction.asDomainModel() }
    }
}

the getEarnings() method defined in the transactionsDao:

@Query("SELECT * FROM transactions WHERE is_income = 1")
fun getEarnings(): Flow<List<DatabaseTransaction>>
kotlin-flow kotlin android
2 Answers

Small add on to philip's answer, In your particular case you can replace the lambda with a callable reference to make the code more concise. this can be done as

.mapIterable(Transaction::asDomainModel)
user_44130980

I've created this extension for the same purpose:

inline fun <T, R> Flow<Iterable<T>>.mapIterable(crossinline transform: (T) -> R): Flow<List<R>> =
    map { it.map(transform) }

Usage:

fun getEarnings(): Flow<List<Transaction>> {
    return transactionDao
        .getEarnings()
        .mapIterable { transaction ->
            transaction.asDomainModel()
        }
}
user_35857960
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