Selection Set - Removing Blocks with a certain name

I am writing an event (reactor) for the erase command. I want to take away the ability for the user to erase certain blocks. I am trying to automatically remove these blocks from a selection set in my erase event. I can't seem to figure this out. How do I automatically remove certain block names from a selection set so they can not be erased. Any Ideas?

 

the ability for the user to erase certain blocks. I am trying to
automatically remove these blocks from a selection set in my erase event. I
can't seem to figure this out. How do I automatically remove certain block
names from a selection set so they can not be erased. Any Ideas?

With a filter, using the NOT key? I'm not certain of the actual code, but
it should be fairly straight forward.

Maybe something like the following:

dim vCod(3) as Integer, vVal(3) as Variant
vCod(0) = -4: vVal(0) = "<NOT"
vCod(1) = 0: vVal(1) = "INSERT"
vCod(2) = 2: vVal(2) = "YourBlockName"
vCod(3) = -4: vVal(3) = "NOT>"
WARNING! I did NOT test this and I'm not even sure if it would work, but I
think the idea is workable.HTH

 

Assuming you were monitoring for the Erase command via the BeginCommand
event, you would have to get the selection set for the command in progress
using ThisDrawing.ActiveSelectionSet. Since this is readonly, you wouldn't
be able to alter the selection set. But if you find the blocks in the active
selection set, you could try canceling the command with:
SendKeys "{ESC}" & "{ESC}"

You might want to prompt the user with info as to why their action wasn't
successful.


--
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Ed
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the ability for the user to erase certain blocks. I am trying to
automatically remove these blocks from a selection set in my erase event. I
can't seem to figure this out. How do I automatically remove certain block
names from a selection set so they can not be erased. Any Ideas?

 

Is it read only as in a pointer to a constant object or read only as in
cannot be assigned to?

 

I did some tests, here's what I found.
TEST1 - this does not error, but also does not alter the ss that is passed
to the erase command so it has no effect.
Private Sub Doc_BeginCommand(ByVal CommandName As String)
Dim ss As AcadSelectionSet
If CommandName = "ERASE" Then
ThisDrawing.ActiveSelectionSet.Clear
ThisDrawing.Utility.Prompt "You are not allowed to erase these
items."
End If
End Sub

TEST2 - This only works if the obects are not selected first. In which case,
you can't test for a block.
Private Sub Doc_BeginCommand(ByVal CommandName As String)
Dim ss As AcadSelectionSet
If CommandName = "ERASE" Then
SendKeys "{ESC}" & "{ESC}"
ThisDrawing.Utility.Prompt "You are not allowed to erase these
items."
End If
End Sub

 

Great Idea!. However I was NOT able to get it to work. Is the syntax of the not operator shown correctly in your snippet? Also why the value of -4? Thanks!

 

So there is NO Solution?

 

You might see if this thread offers any.
http://discussion.autodesk.com/thread.jspa?messageID=384885

 

the not operator shown correctly in your snippet? Also why the value of -4?
Thanks!

It may well be incorrect. I haven't done too much logial testing with
filters in VBA. I'm about 85% sure the idea will work, just not sure of the
code.

Looking at a sample in Joe Sutphin's book, though not exactly like your
situation, would seem to say that it should be more like this:

<AND
<NOT
INSERT
NOT>
<NOT
YourBlockName
NOT>
AND>

If that's not sensible enough, repost and I'll rewrite the whole thing.

 

Thanks for your help but I am still a little confused. When you get a minute could you please post the snippet. Thanks Again.

 

The -4 is a dxf code that allows you to mark the start and end of logical
grouping. However, even if you were to creat a selection set without the
blocks, you still have the problem of preventing their deletion.

--
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Ed
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minute could you please post the snippet. Thanks Again.

 

I think your best bet is to redefine the ERASE command. I threw this
together real quick. It doesn't set any sysvars like cmdecho or check the
pickfirst ss, but should give you an idea. I used lisp because it will make
it easier to redefine using acad.lsp.
(defun c:erase1 ( / ss)
(setq ss (ssget '(
(-4 . "<NOT")
(-4 . "<AND")
(0 . "INSERT")
(2 . "block1");if more than 1 blk "block1,block2"
(-4 . "AND>")
(-4 . "NOT>")
)

)
)
(command "erase" ss "")
)

 

Thanks Ed! This did the trick.