Get a block object, from its name
So, you want to know if a block DEFINITION with certain name(AcadBlock, not AcadBlockReference) exists in the drawing which may contain hundreds of them, or more.
I'd say looping through them to find one, would not be an issue that user would feel noticeable "slowness", unless you need to search many blocks by name with many loops inside loops. That is actually comparing strings (block names, depending how they are named, how long the string be) may cost time. So, I do not see an issue with your code when searching a single block by name (only, why saving the single block definition in a Collection?).
Since block definition (AcadBlock) is stored in block table, keyed by their name, it can be quickly reached by AcadDocument.Blocks(blockName), you code can be shorten and simplified (and run quickly) by
public Function FindBlockDefinition(drawing As AcadDocument, blkName As String) As AcadBlock
On Error Resume Next
Set FindBlockDefinition = drawing.Blocks(blkName)
End Function
Notice that because of "On Error Resume Next", he function would returns Nothing, if a block definition with the given name does not exist.
Again, Letting AutoCAD hits an error and resume to next step may or may not be noticeable fast than loop through the block table, unless there are large numbers of blocks and/or with long block names, and/or having to search in multiple loops.
@george1985 In addition to what @norman.yuan said, you need to realize that the AcadBlocks are already in a collection, ThisDrawing.Blocks. There is only one instance of each definition in the collection and the names are indexed, so a name search is fast. You were putting a block into a new collection. This makes me believe that you have a misunderstanding of the block's api, since there is only one AcadBlock for each block definition. When you say you have 900 blocks in a dwg, I think you mean AcadBlockReference object which are the equivalent of a lisp INSERT object when you use the LIST command. So, I think what you want to do is select a block in the dwg and use the Name property of the insert to get the AcadBlock object representing the block definition. Is that correct? From your first post, it's not clear what your process is. If so, this sample might help you.
Sub Test7()
Dim pp As Variant
Dim ent As AcadEntity
Dim blk As AcadBlock
Dim blkref As AcadBlockReference
ThisDrawing.Utility.GetEntity ent, pp, "Select a block"
If Not ent Is Nothing And ent.ObjectName = "AcDbBlockReference" Then
Set blkref = ent
Set blk = ThisDrawing.Blocks(blkref.EffectiveName) 'works on dynamic blocks too
'do something with the blk
MsgBox "The block's name is " & blk.Name
End If
End SubEd
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I apologize for the late reply. Thank you both of you for the detailed help.
Hi @norman.yuan ,
Brilliant! Thank you very much for the 'drawing.Blocks(blkName)' solution! Indeed it is faster, then iterating through each item in drawing.Blocks.
There is no way to check somehow if 'drawing.Blocks.HasKey(blkName)'?
I see no such method in AcadBlocks class:
Hi @Ed__Jobe ,
Thank you as well for your solution.
I have around 900 normal (non-dynamic) + dynamic block instances (AcadBlockReference objects).
I would like to extract geometry of each of those 900 instances.
For the normal blocks, your solution works perfectly.
The issue are dynamic block instances: Autocad threats each "unique" one of them: as an individual block definition (AcadBlock object). The names of those individual block definitions are "U2", "U3", "U4"...
By "unique" I mean: dynamic block which has unique combination of its parameters (Length, Height, Rotation angle...). But not its attributes.
Because of upper mentioned individual block definition (AcadBlock object) for each unique dynamic block instance - this means that I can't use the .EffectiveName property. I have to find the unique block definition of each unique instance via .Name property.
This was the reason, why I was looking for a faster approach to get the block definition, instead of iterating through the drawing.Blocks.
First, your question regarding a Haskey method, if you ask for the key Name and if doesn’t exist, you get an error. That’s why Norman encapsulated the call in a separate function. His solution is effectively a HasKey function. If it’s there, you get a Block object. If not, you get nothing. Just test the function for return of nothing.
Dim blk As AcadBlock
Set blk = FindBlockDefinition()
If Not blk Is Nothing Then
'Do something with blk
Endif Second, if you have a dynamic block and you want the anonymous block, just use the Name property instead of the EffectiveName property.
Third, to get the attributes , you need to reference the AcadBlockReference object and access its Attributes collection. The AcadBlock object just has a template for the attributes.
Ed
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@george1985 wrote:
Hi @Ed__Jobe
I guess the function encapsulation is specific to VBA. When similar is tried with .NET - the .NET function raises just an error once 'blkName' does not exist in 'drawing.Blocks'
You never mentioned that you were using .net. You still need to trap the error, but you would use a try.catch statement. In one of the catch clauses, you can just ignore the error or return Nothing.
Ed
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