I would use something analogous to a factory method. You're trying to
defer the instantiation of an object to another class that holds the
most appropriate knowledge on which to create. Your code might then
look liked this:
string source =
enrollmentDoc.SelectSingleNod("/EnrollForm/Source").InnerXml.ToUpper;
IStrategy strategy = StrategyFactory.GetStrategy(source);
strategy.DoSomething();
GetStrategy might create the concrete strategy by way of reflection or
you might very well choose to just use a switch statement again if
it's simple; the key difference is that you are delegating the
responsibility of creation to another class, and this affords you an
extra level of extensibility should you continue to add strategies,
sources, etc.
Hope that helps,
Chad
On Fri, 25 Mar 2005 13:06:37 -0500, Bill Bassler
<[EMAIL PROTECTED]> wrote:
> I'm trying to determine the most appropriate design pattern to implement
> for the following problem.
>
> I'm receiving an xml document whose structure contains an element defining
> a source. Each source's document contains a similar but distinct xml
> document. Each one of the distinct documents requires a distinct set of
> message processing steps. I have implemented the document specific
> processing steps/algorithm using the Strategy pattern. This works well at
> cleanly encapsulating the processing logic.
>
> The issue I'm trying to solve is - What's the most appropriate/cleanest way
> to inspect the source element in order to route the xml message to the
> appropriate Strategy for processing. Currently I use a switch statement to
> decide the processing.
>
> e.g.
>
> switch (enrollmentDoc.SelectSingleNod("/EnrollForm/Source").InnerXml.ToUpper
> ())
> {
> case 1:
> // Use Strategy 1
> case 2:
> // Use Strategy 2
> }
>
> This works, but I'm looking for something a little less clunky and
> hopefully more modular. I've looked at the Command pattern ... which seems
> to somewhat fit the task. Possibly the Chain of Command but I don't know
> that I need that level of processing flexiblity as what I need to do can be
> encapsulated pretty well in the Strategy.
>
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