Private vs Public Class Modules

[Ronald R. Dodge, Jr.]

VB6.0
Excel 2002, SP3

How can I get private and public instancing class modules to communicate
with each other?

Example

I am creating a program that using a class name of "TempEmployee" (Need
multiple instances of this class, thus private instance is the only instance
available) and a collection class name of "TempEmployees" (This object, only
need one instance of it and I would like to be able to reference to it from
within any other module within the project, but when I attempt to set a
public variable to it, it comes back stated can't do it as a public variable
can't contain a private class module). I also get the same basic issue with
I attempt to combine public and private classes into each other. What is
the best way to resolve this issue so as I don't have to do so much coding
and work arounds?

One way, I could create properties in so many other objects as a reference
to this one object, on the other hand, that in itself seems to be a lot of
work and could lead to possible overlooking. What is a good book on this
sort of VBA Class module coding?

--
Thanks,

Ronald R. Dodge, Jr.
Production Statistician
Master MOUS 2000

 

[Bob Phillips]

Ronald,

If you want multiple instances of a class, why not create a collection
class? It does mean that you have to code the .Add and .Remove methods, but
it is not difficult.

 

[Ronald R. Dodge, Jr.]

If you notice in the example that I stated, the TempEmployees is the
collection class while the TempEmployee is the Individual object class
similar to the Worksheets collection class with the Worksheet individual
object class.

The TempEmployees collection class is a holder for all of the individual
TempEmployee object classes (One per temporary employee). As such, there
only needs to be one TempEmployees collection object in memory vs several
TempEmployee individual objects in memory.

The problem I'm having, I want to expose this TempEmployees Object to be
visible across the entire project, not just within the module. As it
currently stands, I can only think of using either properties or methods to
set that, which seems to be a lot of work (when you have to do it across
several different classes) that would save some time and prevent possible
overlooking if it could just be set to a variable that could be seen across
the project (I.e. Within VB6, you use the Friend keyword which allows such
cases to be seen outside of the module the code in it, but not outside of
the project the code is in.)

--
Thanks,

Ronald R. Dodge, Jr.
Production Statistician
Master MOUS 2000

 

[Bob Phillips]

Ronald,

I am not getting this. I have just created a class and a collection class,
and setup multiple instances of the first. My collection class variable was
a public variable.

In another module, I accessed this public collection class variable no
problems.

I guess I am not getting the problem?

 

[Ronald R. Dodge, Jr.]

If I set the class to public, I get the below message at compile time:

Private object modules cannot be used in public object modules as parameters
or return types for public procedures, as public data members, or as fields
of public user defined types

and it highlights the following signature line within the public collection
class:

Public Property Get prp_ro_TempEmployeeByID(ByVal l_strIdentificationCode As
String) As clsTempEmployee

As for using "As Object" in place of "As clsTempEmployee", I don't
particularly care for doing that either as that gets away from good
programming practices.


Now when I have the collection class as private, it no longer errors out
during compilation time.

--
Thanks,

Ronald R. Dodge, Jr.
Production Statistician
Master MOUS 2000

 

[Bob Phillips]

Ronald,

Nowhere have I suggested that you set the class instancing type to public, I
used private in both mine. I was talking about creating the collection class
variable as public.

Perhaps it would be best to give the whole code for us to try.

 

[Ronald R. Dodge, Jr.]

As far as declaring variables within class modules as public variables,
that's making implicit statements and not really good programming practices.
I rather use Property statements to expose such things than to use the
Public keyword within variable declarations. The only place where I use
public declarations like that are within standard modules, which I have
attempted to do but still get the same basic issue as I get when attempting
to turn the collection class as a public instance.

This sort of declaration is more or less like the same things as using the
"New" keyword within variable declarations rather than using it within the
procedures when creating new objects. You may think I'm being harsh about
sticking to good programming practices, but I have ran into too many
problems in the past and will only stick to these good programming practices
to avoid many of such issues down the road.

The other thing, I would rather have the class seen by the entire project
than the collection data type variable itself. Reason being, the class
itself has a few things that the collection data type variable doesn't have.
Not only that, but there's greater control over the variables within the
class when it's handled properly within the class. When variables starts
getting handled outside of the class, too many issues are of concern and I
don't care for the risks involved with doing that. Memory leaks is one such
issue like that.

--
Thanks,

Ronald R. Dodge, Jr.
Production Statistician
Master MOUS 2000

 

[Bob Phillips]

As far as declaring variables within class modules as public variables,
that's making implicit statements and not really good programming
practices. I rather use Property statements to expose such things than to
use the Public keyword within variable declarations. The only place where
I use public declarations like that are within standard modules, which I
have attempted to do but still get the same basic issue as I get when
attempting to turn the collection class as a public instance.

Whilst I did not suggest this, there is nothing wrong with it. A public
variable in a class module is a property, it is just an implicit read/write
property.

What I said is to declare the collection class variable as public, that is
the variable in the usage code that links to your collection class.
Somewhere in a standard module I assume you have some code similar in logic
to this pseudo code

Public MyCollClass As CollClass

Public Sub Do Stuff()
Dim MyBasicClass As BasicClass

Set MyCollClass = New CollClass

Set MyBasicClass = New BasicClass
With MyBasicClass

.'populate class instance #1
MyCollClass .Add MyBasicClass
End With
Set MyBasicClass = Nothing

Set MyBasicClass = New BasicClass
With MyBasicClass

.'populate class instance #2
MyCollClass .Add MyBasicClass
End With
Set MyBasicClass = Nothing

Set MyBasicClass = New BasicClass
With MyBasicClass

.'populate class instance #3
MyCollClass .Add MyBasicClass
End With
Set MyBasicClass = Nothing

End Sub


Then you can access each instance through the collection class

This sort of declaration is more or less like the same things as using the
"New" keyword within variable declarations rather than using it within the
procedures when creating new objects. You may think I'm being harsh about
sticking to good programming practices, but I have ran into too many
problems in the past and will only stick to these good programming
practices to avoid many of such issues down the road.

Not at all, I just have no idea how you are doing it. I have outlined above
how I do it.

The other thing, I would rather have the class seen by the entire project
than the collection data type variable itself. Reason being, the class
itself has a few things that the collection data type variable doesn't
have. Not only that, but there's greater control over the variables within
the class when it's handled properly within the class. When variables
starts getting handled outside of the class, too many issues are of
concern and I don't care for the risks involved with doing that. Memory
leaks is one such issue like that.

This I really don't understand. You expose the class through a variable. You
have to provide some means of referencing the class.

I use this technique regularly, and am not aware of any such problems.

 

[Ronald R. Dodge, Jr.]

Okay, this is odd. The last time when I attempted to do just that within a
standard module, it gave me that same basic error message about me not being
able to assign a private class to a public variable. I do it again this
time around and it doesn't error out as I had expected based on previous
experience.
--
Thanks,

Ronald R. Dodge, Jr.
Production Statistician
Master MOUS 2000

 

[Bob Phillips]

So does this mean that you are sorted now?

 

[Ronald R. Dodge, Jr.]

Hopefully, but if this issue comes up again using in this sort of manner, I
will have to post back with the exact message. I have no idea why it failed
on me in prior attempts as I don't recall doing anything different from this
time around.

--
Thanks,

Ronald R. Dodge, Jr.
Production Statistician
Master MOUS 2000

 

[Bob Phillips]

If it does happen again, perhaps mail me the workbook?