clementi clementi - 3 months ago 7
C# Question

Is it OK for a factory method to return null?

I'm wondering about best practice here. Is it good practice for a factory method to return null if it can't create anything? Here's an example:

ICommand command = CommandFactory.CreateCommand(args);
if (command != null)
command.Execute();
else
// do something else if there is no command


An alternative would be to return a
NullCommand
or something, I guess, but what is best practice?

Answer

I think it's potentially reasonable for a factory method to return null in some situations, but not if it's a method called CreateCommand. If it were GetCommand or FetchCommand, that might be okay... but a Create method should throw an exception on failure, I would suggest.

Whether you really want it to return null in this situation depends on the bigger picture, of course. (Is there a reasonable null object implementation you could return instead, for example?)