Mastering Functional Programming

Constructing asynchronous tasks

IO provides an API that allows you to transform an existing computation based on callbacks into an asynchronous IO. This can be used to port existing computation to IO in an asynchronous manner.

Suppose you have the following computation:

def taskHeavy(name: String): Int = {  Thread.sleep(1000)  println(s"${Thread.currentThread.getName}: " +    s"$name: Computed!")  42}

Like we saw previously, it is blocking a thread as it uses Thread.sleep to block the computation. The entire point of the computation is that it does not return immediately.

Now, let's take a look at how you can asynchronously run the computation:

def sync(name: String): IO[Int] =  IO { taskHeavy(name) }

Here, we are using an already familiar ...