{"id":929,"date":"2009-11-24T12:39:29","date_gmt":"2009-11-24T11:39:29","guid":{"rendered":"http:\/\/www.navision-blog.de\/2009\/11\/24\/generating-an-iobservablet-from-an-ievent-in-f\/"},"modified":"2009-12-21T10:34:07","modified_gmt":"2009-12-21T09:34:07","slug":"generating-an-iobservablet-from-an-ievent-in-f","status":"publish","type":"post","link":"http:\/\/www.navision-blog.de\/blog\/2009\/11\/24\/generating-an-iobservablet-from-an-ievent-in-f\/","title":{"rendered":"Generating an IObservable<T> from an IEvent in F#"},"content":{"rendered":"

Yesterday I showed how we can map some of the Rx operators to an API which looks more like the F# base classes<\/a>. Today I wanted to use these mapped operators in a WPF-application written in F#. <\/p>\n

F# gives us a nice way to use events as first class citizen (via IEvent) but these events implement their own version of IObservable<T> (in FSharp.Core.dll), which is unfortunately incompatible with the Rx version and therefore with the mapped API.<\/p>\n

The solution I found is to wrap the F# IEvent with a Rx IObservable<T>:<\/p>\n

\n

\/\/\/ Generates an observable from an IEvent<\/span><\/p>\n

let<\/span> fromEvent (event:IEvent<_,_>) =       <\/p>\n

  Observable.Create<_>(fun<\/span> x -><\/span><\/p>\n

    event.Subscribe x.OnNext |> ignore<\/p>\n

    new<\/span> System.Action(fun<\/span> () -><\/span> ()))      <\/p>\n<\/p><\/div>\n

Now we are able to use the WPF events as observables:<\/p>\n

\n

\/\/ Register ListBox Commands<\/span><\/p>\n

listBox1.KeyDown<\/p>\n

  |> Observable.fromEvent<\/p>\n

  |> Observable.filter (fun<\/span> args -><\/span> args.Key = Key.Delete)<\/p>\n

  |> Observable.subscribe deleteElement<\/p>\n<\/p><\/div>\n

I am interested if someone has a different and maybe better solution to this problem.<\/p>\n

Updated: 21.12.2009 \u2013 Observable.Context is no longer supported by Rx ==> Removed<\/p>\n","protected":false},"excerpt":{"rendered":"

Yesterday I showed how we can map some of the Rx operators to an API which looks more like the F# base classes. Today I wanted to use these mapped operators in a WPF-application written in F#. F# gives us a nice way to use events as first class citizen (via IEvent) but these events […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[448],"tags":[534,579],"_links":{"self":[{"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/posts\/929"}],"collection":[{"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/comments?post=929"}],"version-history":[{"count":1,"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/posts\/929\/revisions"}],"predecessor-version":[{"id":938,"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/posts\/929\/revisions\/938"}],"wp:attachment":[{"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/media?parent=929"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/categories?post=929"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/tags?post=929"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}