Question
"Singleton" factories, ok or bad?
I've a lot of (abstract) factories and they're usually implemented as singletons.
Usually for the convenience of not having to pass them through layers who really have no business with using or knowing these factories.
Most of the times I only need to make a decision at startup of which factory implementation the rest of the code program, maybe through some configuration
it looks e.g. like
abstract class ColumnCalculationFactory {
private static ColumnCalculationFactory factory;
public static void SetFactory(ColumnCalculationFactory f) {
factory = f;
}
public static void Factory() {
return factory;
}
public IPercentCalculation CreatePercentCalculation();
public IAverageCalculation CreateAverageCalculation();
//....
}
Someting do smell about this, I'm just not sure what - it's maybe more a disuised global than a singleton. It's not like there really really have to be only one factory ever creating ColumnCalculations - although my programs don't need more.
Is this considered best practuce ? Should I rather stuff these in some (semi) global AppContext class ? Something else(I'm not quite ready to switch to some larger IoC container, or spring.net quite yet btw) ?