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// ----------------------------------------------------------------------------
// F# async extensions (AsyncSeqObservable.fsx)
// (c) Tomas Petricek, 2011, Available under Apache 2.0 license.
// ----------------------------------------------------------------------------
// This example demonstrates how to convert IObservable<'T> to AsyncSeq<'T>
#r @"..\build\FSharpx.Core.dll"
open FSharp.Control
open System.Windows.Forms
open System.Threading
// Create simple winforms user interface with a button and multiline text box
let frm = new Form(Visible=true, TopMost=true, Width=440)
let btn = new Button(Left=10, Top=10, Width=150, Text="Async Operation")
let out = new TextBox(Left=10, Top=40, Width=400, Height=200, Multiline=true)
// Prints message to the displayed text box
let wprint fmt =
Printf.kprintf (fun s -> out.Text <- out.Text + s) fmt
// The sample demonstrates two ways of converting IObservable<_> values to
// asynchronous sequences. When using 'AsyncSeq.ofObservable', values that are
// emitted when the asynchronous sequence is blocked are discarded. When you
// click on the 'Async Operation' button, the following workflow starts
// processing and drops all clicks until the body of the for loop completes
let discarding =
async {
for click in btn.Click |> AsyncSeq.ofObservable do
wprint "Sleeping (and discarding clicks)...\r\n"
do! Async.Sleep(1000)
wprint "Done (listening again)\r\n" }
let ctsd = new CancellationTokenSource()
Async.Start(discarding, ctsd.Token)
// When using 'AsyncSeq.ofObservableBuffered', the values emitted by the
// observable while the asynchronous sequence is blocked are stored in a
// buffer (and will be returned as next elements).
let buffering =
async {
for click in btn.Click |> AsyncSeq.ofObservableBuffered do
wprint "Sleeping (and buffering clicks)...\r\n"
do! Async.Sleep(1000)
wprint "Done (ready for next value)\r\n" }
let ctsb = new CancellationTokenSource()
Async.Start(buffering, ctsb.Token)
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