Combine

part of kovenant-combine

---

A common case when working with promises is that you want to do something with the results of multiple promises at once. So it would be nice to get notified when those promises are done and do things with the results right away. This is what combine does. It takes from 2 till 20 (arbitrarily chosen) promises and combines them into one new Promise that resolves, when successful, with a Tuple of all results combined. The first of any promise to fail makes the whole promise fail.

val fib20Promise = task { fib(20) }
val helloWorldPromise = task { "hello world" }

combine(fib20Promise, helloWorldPromise) success {
    val (fib, msg) = it
    println("$msg, fib(20) = $fib")
}

and

For the special case of combine with only two parameters there is also an extension method and available. This simply creates nicer looking code and plays well with conciseness fetishists:

task { fib(20) } and task { "hello world" } success {
    println("${it.second}, fib(20) = ${it.first}")
}