Topic: Alternative approaches for Get Dynamic Blocks by Name

[kaefer]

Mark, I think, posted a snippet under http://www.theswamp.org/index.php?topic=31859.msg422435#msg422435 in which the dynamic block references are enumerated by GetBlockReferenceIds(). Which is often not what one would want, e.g. in case of nested and/or unreferenced blocks.

My suggestion uses a custom selection filter (which is one possible way to iterate the model space) and relies on the fact that the anonymous BlockTableRecord corresponding to a dynamic BlockReference has a XData entry which contains the Handle of the unparametrized BlockTableRecord. The upshot is that I'm not comparing names, but only Handles.

Implementation in F#, will port to C# if there's time for and interest in it.
Cheers, Thorsten

Code: [Select]

let (|TypedValue|) (tv: TypedValue) = tv.TypeCode, tv.Value

let tryPickFromXData f (xData: ResultBuffer) =
    if xData = null then None
    else xData.AsArray() |> Array.tryPick f

type Transaction with
    member tr.OpenForRead oid = tr.GetObject(oid, OpenMode.ForRead)
    member tr.TryGetBTRHandleFromDynamicBlockReference oid =
        let br = tr.OpenForRead oid :?> BlockReference

        if br.AnonymousBlockTableRecord.IsNull then
            let btr = tr.OpenForRead br.BlockTableRecord :?> BlockTableRecord
            btr.Handle |> string |> Some
        else
            let btr = tr.OpenForRead br.AnonymousBlockTableRecord :?> BlockTableRecord
            btr.GetXDataForApplication "AcDbBlockRepBTag"
            |> tryPickFromXData
                (fun (TypedValue(k, v)) ->
                    if k = int16 DxfCode.ExtendedDataHandle then string v |> Some
                    else None
                )

type Editor with
    member ed.TrySelectAnonymousBlocks btrHand =
        use tr = ed.Document.Database.TransactionManager.StartTransaction()
       
        let selectionFilter =
            Seq.cast<SelectedObject>
            >> Seq.mapi
                (fun i so ->
                    i, tr.TryGetBTRHandleFromDynamicBlockReference so.ObjectId
                )
            >> Seq.choose
                (function
                    | _, Some hand when hand = btrHand -> None
                    | i, _ -> Some i
                )

        use selectionAdded =
            ed.SelectionAdded
            |> Observable.subscribe
                (fun e ->
                    e.AddedObjects
                    |> selectionFilter
                    |> Seq.iter e.Remove
                )
       
        let sf =
            new SelectionFilter[|
                new TypedValue(int DxfCode.Start, "INSERT") |]
        let pso =
            new PromptSelectionOptions(
                MessageForAdding = "\nSelect block references: " )
        let psr = ed.GetSelection(pso, sf)
        let psr =
            if psr.Status = PromptStatus.Error then ed.SelectAll sf
            else psr
        tr.Commit()
        if psr.Status = PromptStatus.OK && psr.Value.Count > 0 then
            Some psr.Value
        else None

[<CommandMethod "DynBlkSel">]
let dynBlkSel() =
    let ed = acApp.DocumentManager.MdiActiveDocument.Editor
    let db = acApp.DocumentManager.MdiActiveDocument.Database

    use tr = db.TransactionManager.StartTransaction()

    let peo =
        new PromptEntityOptions(
            "\nSelect Blockreference: ", AllowNone = true )
    peo.SetRejectMessage("\nNo Blockreference. ")
    peo.AddAllowedClass(typeof<BlockReference>, false)
    let per = ed.GetEntity peo
   
    if per.Status = PromptStatus.OK then Some per.ObjectId
    else None
    |> Option.bind tr.TryGetBTRHandleFromDynamicBlockReference
    |> function
        | None ->
            ed.WriteMessage("\nCan't find named block. ")
        | Some btrHand ->
            ed.WriteMessage("\nBlock selected with Handle {0}. ", btrHand)
            ed.TrySelectAnonymousBlocks btrHand
            |> function
                | None -> ed.WriteMessage("\nNothing selected. ")
                | Some sset ->
                    ed.WriteMessage("\n{0} blocks selected. ", sset.Count)

    tr.Commit()


[kaefer]

will port to C#

Here we go.

Code: [Select]

    // Demo selection of dynamic blocks that are derived from the same block definition
    public class DynBlkSelCmd
    {
        // Let the user select a single block reference, filter their subsequent selection that
        // it only contains references of the same definition as the one picked first
        [CommandMethod("DynBlkSel")]
        public void DynBlkSel()
        {
            Database db = Application.DocumentManager.MdiActiveDocument.Database;
            Editor ed = Application.DocumentManager.MdiActiveDocument.Editor;
            PromptEntityOptions peo = new PromptEntityOptions("\nSelect Blockreference: ");
            peo.AllowNone = true;
            peo.SetRejectMessage("\nNo Blockreference. ");
            peo.AddAllowedClass(typeof(BlockReference), false);
            PromptEntityResult per = ed.GetEntity(peo);
            if (per.Status != PromptStatus.OK) return;
            using (Transaction tr = db.TransactionManager.StartTransaction())
            {
                if (!TryGetBTRHandleFromDynamicBlockReference(per.ObjectId, out btrHand))
                    ed.WriteMessage("\nCan't find named block. ");
                else
                {
                    ed.WriteMessage("\nBlock selected with Handle {0}. ", btrHand);
                    SelectionSet sset = SelectAnonymousBlocks(ed);
                    if (sset == null)
                        ed.WriteMessage("\nNothing selected. ");
                    else
                        ed.WriteMessage("\n{0} blocks selected. ", sset.Count);
                }
                tr.Commit();
            }
        }

        // Do the actual filtering with a SelectionAdded event handler
        SelectionSet SelectAnonymousBlocks(Editor ed)
        {
            TypedValue[] tva = new TypedValue[] { new TypedValue((int)DxfCode.Start, "INSERT") };
            SelectionFilter sf = new SelectionFilter(tva);
            PromptSelectionOptions pso = new PromptSelectionOptions();
            pso.MessageForAdding = "\nSelect block references (Enter for all): ";
            ed.SelectionAdded += new SelectionAddedEventHandler(SelectionAdded);
            PromptSelectionResult psr = ed.GetSelection(pso, sf);
            if(psr.Status == PromptStatus.Error) psr = ed.SelectAll(sf);
            ed.SelectionAdded -= new SelectionAddedEventHandler(SelectionAdded);
            if(psr.Status == PromptStatus.OK && psr.Value.Count > 0) return psr.Value;
            else return null;
        }

        // Return BTR handle of definition, from Handle property if not dynamic,
        // else from XData of anonymous BTR. Needs active transaction.
        bool TryGetBTRHandleFromDynamicBlockReference(ObjectId oid, out string hand)
        {
            BlockReference br = (BlockReference)oid.GetObject(OpenMode.ForRead);
            hand = null;
            if (br.AnonymousBlockTableRecord.IsNull)
            {
                // Here it's either not a dynamic block or has default parameters only
                BlockTableRecord btr = (BlockTableRecord)br.BlockTableRecord.GetObject(OpenMode.ForRead);
                hand = btr.Handle.ToString();
                return true;
            }
            BlockTableRecord abtr = (BlockTableRecord)br.AnonymousBlockTableRecord.GetObject(OpenMode.ForRead);
            ResultBuffer xData = abtr.GetXDataForApplication("AcDbBlockRepBTag");
            if (xData == null) return false;
            TypedValue[] tva = xData.AsArray();
            for (int i = 0; i < tva.Length; i++)
            {
                if (tva[i].TypeCode == (System.Int16)DxfCode.ExtendedDataHandle)
                {
                    hand = (string)tva[i].Value;
                    return true;
                }
            }
            return false;
        }
             
        void SelectionAdded(object sender, SelectionAddedEventArgs e)
        {
            for(int i = 0; i < e.AddedObjects.Count; i++){
                string hand;
                bool ok = TryGetBTRHandleFromDynamicBlockReference(e.AddedObjects[i].ObjectId, out hand);
                if (!ok || (hand != btrHand)) e.Remove(i);
            }
        }

        string btrHand = null;
    }


[fixo]

Hi Thorsten,
Big thank for the sharing
Regards,

Oleg

[kaefer]

Big thank for the sharing

Don't thank me yet, it's still not the best way. While I started with the Name property, then did away with that as the Handle was sufficient; finally I have found the DynamicBlockTableRecord property. Which can be used for the same end result, filtering block references that point to the same dynamic block definition. Here's the updated code:

Code: [Select]

    // Demo selection of dynamic blocks that are derived from the same block definition
    public class DynBlkSelCmd
    {
        // Let the user select a single block reference, filter their subsequent selection that
        // it only contains references of the same definition as the one picked first
        [CommandMethod("DynBlkSel")]
        public void DynBlkSel()
        {
            Database db = AcApp.DocumentManager.MdiActiveDocument.Database;
            Editor ed = AcApp.DocumentManager.MdiActiveDocument.Editor;
            PromptEntityOptions peo = new PromptEntityOptions("\nSelect Blockreference: ");
            peo.AllowNone = true;
            peo.SetRejectMessage("\nNo Blockreference. ");
            peo.AddAllowedClass(typeof(BlockReference), false);
            PromptEntityResult per = ed.GetEntity(peo);
            if (per.Status != PromptStatus.OK) return;
            using (Transaction tr = db.TransactionManager.StartTransaction())
            {
                btrOid = GetDynamicBlockTableRecordId(per.ObjectId);
                if(btrOid.IsNull)
                    ed.WriteMessage("\nCan't find named block. ");
                else
                {
                    ed.WriteMessage("\nBlock selected with ObjectId {0}. ", btrOid.ToString());
                    SelectionSet sset = SelectAnonymousBlocks(ed);
                    if (sset == null)
                        ed.WriteMessage("\nNothing selected. ");
                    else
                        ed.WriteMessage("\n{0} blocks selected. ", sset.Count);
                }
                tr.Commit();
            }
        }

        // Do the actual filtering with a SelectionAdded event handler
        SelectionSet SelectAnonymousBlocks(Editor ed)
        {
            TypedValue[] tva = new TypedValue[] { new TypedValue((int)DxfCode.Start, "INSERT") };
            SelectionFilter sf = new SelectionFilter(tva);
            PromptSelectionOptions pso = new PromptSelectionOptions();
            pso.MessageForAdding = "\nSelect block references (Enter for all): ";
            ed.SelectionAdded += new SelectionAddedEventHandler(SelectionAdded);
            PromptSelectionResult psr = ed.GetSelection(pso, sf);
            if(psr.Status == PromptStatus.Error) psr = ed.SelectAll(sf);
            ed.SelectionAdded -= new SelectionAddedEventHandler(SelectionAdded);
            if(psr.Status == PromptStatus.OK && psr.Value.Count > 0) return psr.Value;
            else return null;
        }

        // Return BTR Id if not dynamic, else DynamicBlockTableRecord. Needs active transaction.
        ObjectId GetDynamicBlockTableRecordId(ObjectId oid)
        {
            BlockReference br = oid.GetObject(OpenMode.ForRead) as BlockReference;
            if (br == null) return ObjectId.Null;
            if (br.IsDynamicBlock) return br.DynamicBlockTableRecord;
            return br.BlockTableRecord;
        }
             
        void SelectionAdded(object sender, SelectionAddedEventArgs e)
        {
            for(int i = 0; i < e.AddedObjects.Count; i++){
                ObjectId oid = GetDynamicBlockTableRecordId(e.AddedObjects[i].ObjectId);
                if (oid.IsNull || oid != btrOid) e.Remove(i);
            }
        }

        ObjectId btrOid = ObjectId.Null;
    }


[mohnston]

Thanks for your alternative approach. Good to know about the xdata.
And good to have another example of F#.

Your alternative does not get dynamic block references by name. You are asking the user to pick a block and then using that block.
My approach requires only the block name.

[kaefer]

Your alternative does not get dynamic block references by name. You are asking the user to pick a block and then using that block.

Why yes, that was left as an exercise for the reader: Just open the BlockTable and filter for the appropriate BTR ObjectId.

Another improvement may be wrapping the selection in a try-finally-block to ensure removal of the SelectionAdded event handler, however improbable it is that the selection throws an exception. That's why I like Observables: put them in a using statement and the same thing is achieved.

Code: [Select]

    // Demo selection of dynamic blocks that are derived from the same block definition
    public class DynBlkSelByNameCmd
    {
        // Let the user enter a block name, filter their subsequent selection that
        // it only contains references of the same definition
        [CommandMethod("DynBlkSelByName")]
        public void DynBlkSelByName()
        {
            Database db = AcApp.DocumentManager.MdiActiveDocument.Database;
            Editor ed = AcApp.DocumentManager.MdiActiveDocument.Editor;
            PromptStringOptions psto = new PromptStringOptions("\nEnter Block Name: ");
            psto.AllowSpaces = true;
            PromptResult pr = ed.GetString(psto);
            if (pr.Status != PromptStatus.OK) return;
            using (Transaction tr = db.TransactionManager.StartTransaction())
            {
                BlockTable bt = (BlockTable)tr.GetObject(db.BlockTableId, OpenMode.ForRead);
                if (!bt.Has(pr.StringResult))
                {
                    ed.WriteMessage("\n{0} not defined. ", pr.StringResult);
                    return;
                }
                btrOid = bt[pr.StringResult];
                SelectionSet sset = SelectAnonymousBlocks(ed);
                if (sset == null)
                    ed.WriteMessage("\nNothing selected. ");
                else
                    ed.WriteMessage("\n{0} blocks selected. ", sset.Count);
                tr.Commit();
            }
        }

        // Do the actual filtering with a SelectionAdded event handler
        SelectionSet SelectAnonymousBlocks(Editor ed)
        {
            TypedValue[] tva = new TypedValue[] { new TypedValue((int)DxfCode.Start, "INSERT") };
            SelectionFilter sf = new SelectionFilter(tva);
            PromptSelectionOptions pso = new PromptSelectionOptions();
            pso.MessageForAdding = "\nSelect block references (Enter for all): ";
            ed.SelectionAdded += new SelectionAddedEventHandler(SelectionAdded);
            try
            {
                PromptSelectionResult psr = ed.GetSelection(pso, sf);
                if (psr.Status == PromptStatus.Error) psr = ed.SelectAll(sf);
                if (psr.Status == PromptStatus.OK && psr.Value.Count > 0) return psr.Value;
                else return null;
            }
            finally
            {
                ed.SelectionAdded -= new SelectionAddedEventHandler(SelectionAdded);
            }
        }

        // Return BTR Id if not dynamic, else DynamicBlockTableRecord. Needs active transaction.
        ObjectId GetDynamicBlockTableRecordId(ObjectId oid)
        {
            BlockReference br = oid.GetObject(OpenMode.ForRead) as BlockReference;
            if (br == null) return ObjectId.Null;
            if (br.IsDynamicBlock) return br.DynamicBlockTableRecord;
            return br.BlockTableRecord;
        }
             
        void SelectionAdded(object sender, SelectionAddedEventArgs e)
        {
            for(int i = 0; i < e.AddedObjects.Count; i++){
                ObjectId oid = GetDynamicBlockTableRecordId(e.AddedObjects[i].ObjectId);
                if (oid.IsNull || oid != btrOid) e.Remove(i);
            }
        }

        ObjectId btrOid = ObjectId.Null;
    }