SQLDelight Kotlin Multiplatform Project sample

0_common.kt

internal expect fun <B> backToFront(b: () -> B, job: (B) -> Unit)

1_android.kt

private val btfHandler = Handler(Looper.getMainLooper())

internal actual fun <B> backToFront(b: () -> B, job: (B) -> Unit) {
    btfHandler.post { job(b()) }
}

2_ios.kt

internal actual fun <B> backToFront(b: () -> B, job: (B) -> Unit) {
    dispatch_async_f(
        dispatch_get_main_queue(),
        DetachedObjectGraph { JobAndThing(job.freeze(), b()) }.asCPointer(),
        staticCFunction { p: COpaquePointer? ->
            initRuntimeIfNeeded()
            @Suppress("UNCHECKED_CAST") val result = DetachedObjectGraph<Any>(p).attach() as JobAndThing<B>
            result.job(result.thing)
        })
}

QueryExtensions.kt

import com.codingfeline.github.platform.backToFront
import com.squareup.sqldelight.Query
import kotlinx.coroutines.ExperimentalCoroutinesApi
import kotlinx.coroutines.channels.Channel
import kotlinx.coroutines.channels.consumeEach
import co.touchlab.stately.concurrency.ThreadLocalRef

@ExperimentalCoroutinesApi
fun <T : Any> Query<T>.asChannel(): ReceiveChannel<Query<T>> {
    val channel = Channel<Query<T>>(Channel.CONFLATED)
    channel.offer(this)

    val ref = ThreadLocalRef<(Query<T>) -> Unit>()
    ref.set { channel.offer(it) }

    val listener = object : Query.Listener, (Throwable?) -> Unit {
        override fun queryResultsChanged() {
            backToFront({ this@asChannel }, { q -> ref.get()?.let { it(q) } })
        }

        override fun invoke(t: Throwable?) {
            ref.remove()
            removeListener(this)
        }
    }

    addListener(listener)
    channel.invokeOnClose(listener)

    return channel
}