//arrow-fx-stm/arrow.fx.stm/STM/write

write

common abstract fun <A> TVar<A>.write(a: A)

Set the value of a TVar.

import arrow.fx.stm.TVar
import arrow.fx.stm.atomically

suspend fun main() {
  //sampleStart
  val tvar = TVar.new(10)
  val result = atomically {
    tvar.write(20)
  }
  //sampleEnd
  println(result)
}

Similarly to read this comes with a few guarantees:

  • For multiple writes to the same TVar in a transaction only the last will actually be performed
  • When committing the value inside the TVar, at the time of calling write, has to be the same as the current value otherwise the transaction will retry

common open fun <A> TQueue<A>.write(a: A)

Append an element to the TQueue.

import arrow.fx.stm.TQueue
import arrow.fx.stm.atomically

suspend fun main() {
  //sampleStart
  val tq = TQueue.new<Int>()
  atomically {
    tq.write(2)
  }
  //sampleEnd
  println("Items in queue ${atomically { tq.flush() }}")
}

This function never retries.

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