Can inherited code call derived code? If so how.
I have identical 'generic' code that I am repeating again and again
in several derived form because I don't know how to get inherited
code to call derived code. Am I stuck with this situation or is there a
way around it? Below is some sample code.
=============== ===============
Private Sub LoadDataInForm( ) '= Form_Load
Call FillDataSet()
Call CreateBindings( )
Call DataEntryContro lsAccessible(Fa lse)
Call HideDgColumns()
Call NewCancelSaveCl oseButtonState( "NewClose")
End Sub
Private Sub RemoveRow() ' RemoveAt button
_bmb.RemoveAt(_ bmb.Position)
Call DataEntryContro lsAccessible(Fa lse)
Call NewCancelSaveCl oseButtonState( "NewClose")
Call UpdateDataSet()
End Sub
=============== ===============
Most of the calls call code in the derived forms.
Is there a way around duplicating this code in every form?
- Doug
3  1503 
dbuchanan,
| Can inherited code call derived code? If so how.
It sounds like you wan to use the Template Method pattern.
In your base form define the method to call Overridable methods that the
derived form overrides.
Something like:
Public Class BaseForm
Inherits System.Windows. Forms.Form
| Private Sub LoadDataInForm( ) '= Form_Load
| Call FillDataSet()
| Call CreateBindings( )
| Call DataEntryContro lsAccessible(Fa lse)
| Call HideDgColumns()
| Call NewCancelSaveCl oseButtonState( "NewClose")
| End Sub
Protected Overridable Sub FillDataSet()
Throw New NotImplementedE xception()
End Sub
Protected Overridable Sub CreateBindings( )
Throw New NotImplementedE xception()
End Sub
...
End Class
Public Class DerivedForm
Inherits BaseForm
Protected Overrides Sub FillDataSet()
' fill the data set object
End Sub
Protected Overrides Sub CreateBindings( )
' create the data bindings
End Sub
...
End Class
Depending on the requirements of the Template method & the base class I will
make the stub routines (FillDataSet & CreateBindings) MustOverride instead
of Overridable as the derived class is required to override them, however in
the case of a Form, you cannot use MustOverride as it interferes with the
designer... using a couple "#if debug" you can have the method MustOverride
in the release builds & Overridable in the debug builds...
Hope this helps
Jay
"dbuchanan" <db*********@ho tmail.com> wrote in message
news:11******** **************@ o13g2000cwo.goo glegroups.com.. .
| Can inherited code call derived code? If so how.
| I have identical 'generic' code that I am repeating again and again
| in several derived form because I don't know how to get inherited
| code to call derived code. Am I stuck with this situation or is there a
| way around it? Below is some sample code.
| =============== ===============
| Private Sub LoadDataInForm( ) '= Form_Load
| Call FillDataSet()
| Call CreateBindings( )
| Call DataEntryContro lsAccessible(Fa lse)
| Call HideDgColumns()
| Call NewCancelSaveCl oseButtonState( "NewClose")
| End Sub
|
| Private Sub RemoveRow() ' RemoveAt button
| _bmb.RemoveAt(_ bmb.Position)
| Call DataEntryContro lsAccessible(Fa lse)
| Call NewCancelSaveCl oseButtonState( "NewClose")
| Call UpdateDataSet()
| End Sub
| =============== ===============
| Most of the calls call code in the derived forms.
| Is there a way around duplicating this code in every form?
|
| - Doug
|
Jay,
It works!
You refer to the "template method" pattern. Where can I learn more
about this and other patterns?
Thank you.
-Doug
Doug,
The "Template Method" pattern is defined in the Gang of Four's (GOF) book
"Design Patterns - Elements of Reusable Object-Oriented Software" from
Addison Wesley, it is IMHO a "must have" book for the serious OO developer.
Design Patterns provide programmers with a convenient way to reuse
object-oriented code & concepts amount programmers and across projects,
offering easy, time-saving solutions to commonly recurring problems in
software design. The GOF are Erich Gamma, Richard Helm, Ralph Johnson, and
John Vlissides.
James W. Cooper's book "Visual Basic Design Patterns - VB 6.0 and VB.NET" is
also a "must have" book that is an excellent companion to the above GOF
book. Cooper's book gives the VB6 & VB.NET view of each pattern in the GOF
book.
I would ultimately recommend both books. However! If you can't afford both
of the above books I would recommend the first if you can read & understand
C++, otherwise I would recommend the second if you only can read &
understand VB...
The C# version of Cooper's book was available on the internet, not sure if
it still is. There are numerous sites (some better then others) that cover
the above design patterns & others...
Hope this helps
Jay
"dbuchanan" <db*********@ho tmail.com> wrote in message
news:11******** **************@ o13g2000cwo.goo glegroups.com.. .
| Jay,
|
| It works!
|
| You refer to the "template method" pattern. Where can I learn more
| about this and other patterns?
|
| Thank you.
| -Doug
|
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