On Apr 23, 2006, at 2:10 PM, Marc Van Olmen wrote:
Am 23.04.2006 um 19:05 schrieb Marc Van Olmen:
Not familiar with Factory, any URL's where i can find more info
about this,
http://en.wikipedia.org/wiki/Factory_method_pattern
Hans-Georg
Good Description, I wasn't familiar with term, anyway it seems I
was doing currently with "select case..." is Factory pattern.
It is. For reasons of performance and code maintainability, you
might move from a Select Case block to something fancier. For
example, you could do something like the following. Define a class
ObjectFactory with a method NewObject(className as String) as
Variant. Inside the class, you have a private property CreatorMap as
Dictionary. Then the function is implemented like so.
Function NewObject(className as String) as Variant
If CreatorMap.HasKey(className) then
dim creator as ObjectCreator = CreatorMap.value(className)
Return objectCreator.NewObject
Else
Return nil
End if
End Function
ObjectCreator is a class interface with a single method NewObject()
as Variant. You implement this interface in classes like
WidgetObjectCreator.
Function NewObject() as Variant
Return new Widget
End Function
You populate the CreatorMap Dictionary above at some point before
using the ObjectFactory.
One advantage of such an approach is that you can add or remove
ObjectCreators without having to rewrite ObjectFactory code.
There are other ways to implement this pattern, depending on your
needs. The addition of shared methods to REALbasic provides other
options.
Charles Yeomans
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