concurrency - How to add callbacks to Future in Scala? -


i saw example here:

 val fut = future { ... // body function } // body function starts here fut oncomplete { ... // callback }

looks may add callback after completion of body function. still invoked ? anyway, prefer add callbacks future before function starts running. make sense ? how can ?

if want control point of execution of future, chain promise.

import scala.concurrent._ import executioncontext.implicits.global  val initialpromise = promise[unit]  // add computations val fut = initialpromise.future map { _ => println("my future") }  // register callbacks fut oncomplete { _ => println("my callback") }  // run initialpromise.success()

using other unit allows feed computation arbitrary values.


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