How to start autocad from VB (not VBA)

Is it possible to start autocad from VB open a drawing and switch to one of the layouts saves within the drawing.

Thanks
P. de Boer

 

Sure thing, here's how it's done.


Dim oAcadApp As AcadApplication

If LoadAutoCAD(oAcadApp) Then
With oAcadApp
.ActiveDocument.ActiveLayout =
oAcadApp.ActiveDocument.Layouts("Layout1")
End With
End If


Public Function LoadAutoCAD(oApp As AcadApplication) As Boolean
On Error Resume Next

'try to get running instant of AutoCAD
Set oApp = GetObject(, "AutoCAD.Application")

If Err Then
Err.Clear

Set oApp = CreateObject("AutoCAD.Application")

'exit function, no AutoCAD available
If Err Then Exit Function
End If

'AutoCAD instant open, make it visible
oApp.Visible = True
'return True that AutoCAD was opened successfully
LoadAutoCAD = True
End Function

of the layouts saves within the drawing.

 

VBA,
What is this LoadAutoCAD() function?
Kenneth Hutson
San Antonio, TX

 

It's with the code I posted, look down the page.

 

I noticed it never returns False.

 

It sure does, all functions return False by default. If I didn't have the
LoadAutoCAD = True statement in there it would return False, hence the
statement.

 

I can't say it's a good idea to rely on such things. It's also not at
all obvious. Why not just actually return False rather than exiting the
function?

 

It's been this way since the beginning of VB. It's not like C/C++. I have
done it this way for years and years and I have never had any reason even
remotely requiring otherwise.

 

You're not interested in self-documenting code? Very well then.

 

It's really pretty self-explanatory. It's standard VB language usage, not
rocket science.

 

Obviously not. I'm not trying to pick a fight or put you down. I'm just
pointing out that your code requires the reader to understand a feature
of the language when it could just as easily make itself plainly evident:

If Err Then LoadAutoCAD = False

That's it. I've been working with VB since version 3 and have never
heard that a function returns False by default. Even now, I'm sure
that's an oversimplification. It's far more likely functions return the
default value for their return type if exited without an explicit return
value.

 

BTW, far from trying to imply you may be incorrect, I was pointing out
that I honestly did not know about default return values despite my
experience with the language.

It's reasonable to assume others may not be aware of that feature as well.

 

Actually, I did misspeak a bit when I said all functions.

I should have said all functions whos return datatype is Boolean.

It's the same principle as when you are declaring variables.

Dim X As Boolean

X's initial value is set to False.

That's why I don't understand why it's such a big deal to leave it out of
the function.

 

That's why I don't understand why it's such a big deal to leave it out of

FWIW following a self documented regime would require you to set the
function to false instead of leaving it implied. For example, if you leave
your company and your replacement opens your code, he may not realize that
the function returns false because the VB documentation does not explicitly
state that. Been down that road with clients that purchase source code, so
now its second nature to add it.

-- Mike
___________________________
Mike Tuersley
CADalyst's CAD Clinic
Rand IMAGINiT Technologies
___________________________
the trick is to realize that there is no spoon...

 

From the VB help files

To return a value from a function, assign the value to the function name.
Any number of such assignments can appear anywhere within the procedure. If
no value is assigned to name, the procedure returns a default value: a
numeric function returns 0, a string function returns a zero-length string
(""), and a Variant function returns Empty. A function that returns an
object reference returns Nothing if no object reference is assigned to name
(using Set) within the Function.

 

Hi,

I speak from having knowledge of the features since the VB1 era, but still
use the set to false my code by habit and for self-documentation.

Clearly it is a personal thing.

--

Regards,


Laurie Comerford
www.cadapps.com.au

 

I personally do the same as VBA. For those of you who don't, Mikey, do you
do this?

Dim i as integer
i = 0
for i = 0 to somecollection.count
'blah
next


Scott

 

....and just so you don't nit pick...

for i = 0 to Ubound(somearray)

but you get the idea....

 

That's a waste of time considering you're going to set the value in your
very next line of code.

I used to do that all the time. It's inefficient as the property must be
queried with each iteration. Now I do this:

' When knowing an item index is handy
Dim min As Long, max As Long, i As Long
min = LBound(array)' or 1 for collections
max = UBound(array)' or <collection>.Count
For i = min To max
' Do your thing
Next

Or this:

'When an index is not desired.
For Each <objectType> In <collection>
' Do your thing
Next

BTW, VB arrays support iteration so long as your enumeration variable is
of type Variant.

 

Frank,

I understand and agree with your thoughts, but the idea was more simplistic.
I should have stated:

Dim i as integer
i = 0
i = 10 + 2

Believe it or not, I see this in a lot of code.

Getting back to the original thread - if you initialize a variable as
boolean datatype that variable has a value - false, we all know that. A
function is no different - as boolean = false. There's no need to
explicitly set it = false. I see so much code where a function is defined
as a boolean and the very FIRST line of code is 'FunctionName'= False.

So the point is - if you initialize a var as boolean it = false. why set it
to false???

I'm just advocating VBA's approach to this. As I have done this for years
without issues. If a programmer looks at my code in 2 years doesn't
understand what is being returned then he needs some training.

Scott