我想了解一下最佳实践在这里。它是很好的做法的工厂方法返回null,如果它不能创造什么?这里有一个例子:
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
另一种方法是返回一个 NullCommand
什么的,我猜,但什么是最好的做法?
An alternative would be to return a NullCommand
or something, I guess, but what is best practice?
推荐答案
我认为这是可能合理的工厂方法在某些情况下返回null,但是的没有的,如果它是一个名为方法 CreateCommand
。如果是 GetCommand
或 FETCHCOMMAND
,这可能是正确的......但创建
方法应该抛出故障异常,我会建议。
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.
无论你的真正的希望它返回空
在这种情况下当然取决于大局观。 (是否有一个合理的空对象实现,你可以返回来代替,比如?)
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?)
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