Topic: Multiple Options in SelectionFilter

[David Hall]

What I want to do is offer 2-8 options for a filter, and I know I've seen it, but I can't find the post showing it.  Something similiar to this

Code: [Select]

TypedValue[]  filter = { new TypedValue((int)DxfCode.Start , "INSERT"),new TypedValue (2,"TEP-INFO", "UES-INFO") };Of course it crashes as soon as I add the second string value

[David Hall]

Found it here  Thanks Kerry

[T.Willey]

Was just about to post this link.  Another one from Kerry.

http://www.theswamp.org/index.php?topic=21930.msg264791#msg264791

[David Hall]

Thanks Tim!  both are good examples of multiple choices.

[gile]

Hi,

You can have a look here too.

[T.Willey]

Hi,

You can have a look here too.

They asked for a username/password.

[David Hall]

Yea that looks like a new site that started after the fall of AUGI

[Kerry]

Yea that looks like a new site that started after the fall of AUGI

before, actually.

Found it here  Thanks Kerry

You're most welcome.
I'm in parenthesis land mostly these days ... looking forward to using braces again soon.

[kaefer]

Brace yourself. I'd recommend the SelectionAdded event for filtering that's more than usually complicated.
Say we want to select Polylines with 100 < length <= 300 that are red and on layers FOO or BAR.

Exhibit #1: The straightforward C# approach.

Code: [Select]

    public class SelectionAddedCmd
    {
        bool myFilter(DBObject dbo)
        {
            var pl = dbo as Polyline;
            return
              pl != null &&
              pl.Length > 100.0 &&
              pl.Length <= 300.0 &&
              pl.ColorIndex == 1 &&
              pl.Layer == "FOO" ||
              pl.Layer == "BAR";
        }
        void selectionAdded(object sender, SelectionAddedEventArgs e)
        {
            var i = 0;
            foreach (SelectedObject so in e.AddedObjects)
            {
                if (!myFilter(so.ObjectId.GetObject(OpenMode.ForRead)))
                    e.Remove(i);
                i++;
            }
        }
        PromptSelectionResult selectWithFilter(Editor ed)
        {
            try
            {
                ed.SelectionAdded += new SelectionAddedEventHandler(selectionAdded);
                return ed.GetSelection();
            }
            finally
            {
                ed.SelectionAdded -= new SelectionAddedEventHandler(selectionAdded);
            }
        }
       
        [CommandMethod("SELFILC")]
        public void SelFilC()
        {
            var doc = acApp.DocumentManager.MdiActiveDocument;
            var db = doc.Database;
            var ed = doc.Editor;

            using (Transaction tr = db.TransactionManager.StartTransaction())
            {
                var psr = selectWithFilter(ed);
                if (psr.Status == PromptStatus.OK && psr.Value.Count > 0)
                    ed.WriteMessage("\n{0} Objects selected", psr.Value.Count);
                else
                    ed.WriteMessage("\nNo Objects selected. ");
            }
        }
    }

Drawback: the predicate myFilter is hardcoded into the event handler. Compare this to

Exhibit #2: the F# proposal.

Code: [Select]

let (+=) e f = Observable.subscribe f e

let selectionIndexed =
    Seq.cast<SelectedObject> >> Seq.mapi (fun i so -> i, so.ObjectId)

let myFilter: DBObject->_ = function
    | :? Polyline as pl ->
        pl.Length > 100. &&
        pl.Length <= 300. &&
        pl.ColorIndex = 1 &&
        pl.Layer = "FOO" ||
        pl.Layer = "BAR"
    | _ -> false

let selectWithFilter (ed: Editor) f =
    use selectionAdded =
        ed.SelectionAdded +=
            fun e ->
                for (i, oid) in selectionIndexed e.AddedObjects do
                    if oid.GetObject OpenMode.ForRead |> f |> not then
                        e.Remove i
    ed.GetSelection()

[<CommandMethod "SELFILF">]
let selFilF() =
    let doc = acApp.DocumentManager.MdiActiveDocument
    let db = doc.Database
    let ed = doc.Editor
    use tr = db.TransactionManager.StartTransaction()

    let psr = selectWithFilter ed myFilter
    if psr.Status = PromptStatus.OK && psr.Value.Count > 0 then
        ed.WriteMessage("\n{0} Objects selected", psr.Value.Count)
    else
        ed.WriteMessage("\nNo Objects selected. ")

Now trying to replicate this in C# brings me into RX land, but it ain't very pretty.

Exhibit #3:

Code: [Select]

        ...
        void selectionAdded(SelectionAddedEventArgs e, Func<DBObject, bool> f)
        {
            var i = 0;
            foreach (SelectedObject so in e.AddedObjects)
            {
                if (!f(so.ObjectId.GetObject(OpenMode.ForRead)))
                    e.Remove(i);
                i++;   
            }
        }
        PromptSelectionResult selectWithFilter(Editor ed, Func<DBObject, bool> f)
        {
            IObservable<IEvent<SelectionAddedEventArgs>> selectionAddedAsObservable =
                    Observable.FromEvent<SelectionAddedEventHandler,SelectionAddedEventArgs>(
                        e => new SelectionAddedEventHandler(e),
                        h => ed.SelectionAdded += h,
                        h => ed.SelectionAdded -= h);
            using( var selectionAddedDisposable = selectionAddedAsObservable.Subscribe(a => selectionAdded(a.EventArgs, f))){
                return ed.GetSelection();
            }
        }
        ...
        var psr = selectWithFilter(ed, myFilter);
        ...

Any other suggestions to allow passing the predicate function to the event handler?

Greetings, Thorsten