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Our journey to F#: making async understand Tasks

 4 years ago
source link: https://www.planetgeek.ch/2021/04/22/our-journey-to-f-making-async-understand-tasks/
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Our journey to F#: making async understand Tasks

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In our F# code, we have a lot of asynchronicity: query the DB, call external services, write messages to the service bus, etc. Inside of our happy F# bubble we use async workflows, either by using Async or by using the computation expression async { ... }. But we are surrounded by a world of Tasks. So we often need to call functions or methods that return a Task. Of course, that is no big problem, we can just add |> Async.AwaitTask, but that leads to a lot of visual clutter in our precious business logic code. And it’s very easy to extend the async { } computation expression to do it for us.

Instead of writing

let foo () =
    async {
        let! bar = Bar.get () |> Async.AwaitTask
        // do some stuff
        return result;
    }

we would like to write

let foo () =
    async {
        let! bar = Bar.get ()
        // do some stuff
        return result;
    }

because the noise of switching from Task to Async disappears.

To achieve this, we added the following module to our code base:

[<AutoOpen>]
module Calitime.TimeRocket.AsyncCE

open System.Threading.Tasks

/// extends the async CE to allow awaiting tasks
type AsyncBuilder with
    member x.Bind(task : Task<'a>, f : 'a -> Async<'b>) =
        let task = task |> Async.AwaitTask
        async.Bind(task, f)

The module above simply extends the AsyncBuilder with an additional method that handles banging (!) tasks.

Find all blog posts about our journey to F# here.

This blog post is made possible with the support of Time Rocket, the product this journey is all about. Take a look (German only).


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