arrow-fx-stm/arrow.fx.stm/STM/tryRead

tryRead

open fun <A> TMVar<A>.tryRead(): A?

Same as TMVar.read except that it returns null if the TMVar is empty and thus never retries.

import arrow.fx.stm.TMVar
import arrow.fx.stm.atomically

suspend fun main() {
  //sampleStart
  val tmvar = TMVar.empty<Int>()
  val result = atomically {
    tmvar.tryRead()
  }
  //sampleEnd
  println("Result $result")
}
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See also

for a function that retries if the TMVar is empty.

for a function that leaves the TMVar empty after reading.

open fun <A> TQueue<A>.tryRead(): A?

Same as TQueue.read except it returns null if the TQueue is empty.

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

suspend fun main() {
  //sampleStart
  val tq = TQueue.new<Int>()
  val result = atomically {
    tq.tryRead()
  }
  //sampleEnd
  println("Result $result")
  println("Items in queue ${atomically { tq.flush() }}")
}
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This function never retries.