Event.partition<'T,'Del> Function (F#)

Returns a new event that listens to the original event and triggers the first resulting event if the application of the predicate to the event arguments returned true, and the second event if it returned false.

Namespace/Module Path: Microsoft.FSharp.Control.Event

Assembly: FSharp.Core (in FSharp.Core.dll)

// Signature:
Event.partition : ('T -> bool) -> IEvent<'Del,'T> -> IEvent<'T> * IEvent<'T> (requires delegate)

// Usage:
Event.partition predicate sourceEvent

Parameters

• predicate
  Type: 'T -> bool

  The function to determine which output event to trigger.

• sourceEvent
  Type: IEvent<'Del,'T>

  The input event.

Return Value

A tuple of events. The first is triggered when the predicate evaluates to true and the second when the predicate evaluates to false.

Remarks

This function is named Partition in compiled assemblies. If you are accessing the function from a language other than F#, or through reflection, use this name.

Example

The following code shows how to use the Event.partition function to split an event into two events, each with its own event handling code.

open System.Windows.Forms
open System.Drawing

let form = new Form(Text = "F# Windows Form",
                    Visible = true,
                    TopMost = true)

let (event1, event2) =
    form.MouseMove 
    |> Event.partition (fun evArgs -> evArgs.X > 100)

event1 |> Event.add ( fun evArgs ->
    form.BackColor <- System.Drawing.Color.FromArgb(
        evArgs.X, evArgs.Y, evArgs.X ^^^ evArgs.Y))
event2 |> Event.add ( fun evArgs ->
    form.BackColor <- System.Drawing.Color.FromArgb(
        evArgs.Y, evArgs.X, evArgs.Y ^^^ evArgs.X))

Platforms

Windows 7, Windows Vista SP2, Windows XP SP3, Windows XP x64 SP2, Windows Server 2008 R2, Windows Server 2008 SP2, Windows Server 2003 SP2

Version Information

F# Runtime

Supported in: 2.0, 4.0

Silverlight

Supported in: 3

See Also

Reference

Control.Event Module (F#)

Microsoft.FSharp.Control Namespace (F#)

Change History

Date	History	Reason
September 2010	Added code example.	Information enhancement.