Using public members of a class inside the class

[Guillermo López-Anglada]

Hello,

I have a class like this:

'Class module

Public Property Get GetTextFromRange() as String
'Code
End Property

Public Function ProcessText() as String

'For example:
ProcessText = Left$(Me.GetTextFromRange,5)


End Sub
'End of Class module

Is it a good practice to use public members of a class like that?

Regards,

Guillermo

 

[Jezebel]

No reason why not. It's even fairly common: you have some standard function
that you use throughout the app; it's just as useful from within the module
as elsewhere; and for consistency's sake it's better, as far as possible,
always to use the same method.

You don't need the 'me', BTW. And your example looks more like a function
than a property.

 

[Guillermo López-Anglada]

I mainly used the "me" qualifier for clarity, but actually it would seem that it saves you some typing as well in the IDE...

I have no formal training in programming, but isn't the difference between functions and properties a matter of
preference to a certain extent? I mean, in my particular case, my property ·always· retrieves its value from the same
range... Anyway, I'd very much like to hear any brief explanation on the topic.

Thanks,

Guillermo

 

[Jezebel]

You're right about functions and properties being to some extent a matter of
preference; but there is an important conceptual difference in
object-oriented programming (which is what you are doing with VBA).

Properties are values, derived by calculation perhaps, but essentially
static. They can be set as well as read (unless you choose to make the read-
or write-only). When you query a property, you are asking for some
information about the thing that has that property. In your example,
GetTextFromRange isn't a property of anything (and it would make no
difference where you put the function); nor would it make any sense to *set*
the GetTextFromRange property.

Functions are methods. They are an instruction to *do* something. If the
something is to perform a calculation, then the effect is -- as you
observe -- essentially the same as a property.

Consider the objects of Word itself. If you look at the documentation, each
object has properties and methods. The methods are coded as functions.

 

[Guillermo López-Anglada]

Hi Jezebel,

Thank you for your explanation.

This thread is gone off-topic, but still I'd like to make a final remark. In my program, my class sets and reads the
text in several cells of a table placed in a document it describes. Thus, I have coded the property GetTextFromRange()
as read/write. When you say that it rather looks like a function I wonder if it's because of the (misleading) identifier
I used, which implies an process. In actuality, I think it would be more appropriate to write the whole thing as follows:

'Class module
Public Property Let TargetText (StringA as String)

StringA = Trim(StringA)
Activedocument.Tables(1).Columns(2).Cells(3).Range.Text = StringA

End Property

Public Property Get TargetText () as String

TargetText = Activedocument.Tables(1).Columns(2).Cells(3).Range.Text

End Property
'End of class module

This way it is clearer that the code mainly manipulates a property. Would you still implement it as a function instead?

Regards,

Guillermo

You're right about functions and properties being to some extent a matter of
preference; but there is an important conceptual difference in
object-oriented programming (which is what you are doing with VBA).

Properties are values, derived by calculation perhaps, but essentially
static. They can be set as well as read (unless you choose to make the read-
or write-only). When you query a property, you are asking for some
information about the thing that has that property. In your example,
GetTextFromRange isn't a property of anything (and it would make no
difference where you put the function); nor would it make any sense to *set*
the GetTextFromRange property.