kuilt-quilter/us.tractat.kuilt.quilter/Quilter/mutate

mutate

fun mutate(transform: (S) -> Patch<S>)

Apply a local mutation expressed as a transform on the current state. Equivalent to apply(state.value.let(transform)) but avoids reading state.value at every call site.

tally.mutate { it.increment(replica, 3L) }

Throws

IllegalStateException

if this replicator has been closed.

Samples

runTest(
    StandardTestDispatcher(),
    timeout = 5.seconds,
) {
    val loom = InMemoryLoom()
    val seamAlice = loom.host(Pattern("vote-tally"))
    val seamBob = loom.join(InMemoryTag("bob"))

    // No manual QuiltMessage.serializer(...) wrapping needed.
    val cfg = QuilterConfig(expectVirtualTime = true)
    val aliceTally = Quilter(seamAlice, PNCounter.ZERO, PNCounter.serializer(), backgroundScope, config = cfg)
    val bobTally = Quilter(seamBob, PNCounter.ZERO, PNCounter.serializer(), backgroundScope, config = cfg)

    kotlinx.coroutines.delay(1)

    // mutate removes the state.value repetition at every call site.
    aliceTally.mutate { it.increment(aliceTally.replica, 3L) }
    bobTally.mutate { it.decrement(bobTally.replica, 1L) }

    kotlinx.coroutines.delay(10)

    assertEquals(2L, aliceTally.state.value.value)
    assertEquals(aliceTally.state.value.value, bobTally.state.value.value)
}