这绝对是主观的,但我想尽量避免它变成争论。我认为如果人们恰当地对待它,这将是一个有趣的问题。
这个问题的想法来自于我对“你最讨厌的语言的哪五件事?”问题的回答。我认为c#中的类在默认情况下应该是密封的——我不会把我的理由放在这个问题上,但我可能会写一个更完整的解释来回答这个问题。我对评论中的讨论热度感到惊讶(目前有25条评论)。
那么,你有什么有争议的观点?我宁愿避免那些基于相对较少的基础而导致相当宗教的事情(例如,大括号放置),但例如可能包括“单元测试实际上并没有多大帮助”或“公共字段确实是可以的”之类的事情。重要的是(至少对我来说)你的观点背后是有理由的。
请提出你的观点和理由——我鼓励人们投票给那些有充分论证和有趣的观点,不管你是否恰好同意这些观点。
好吧,我说过我会更详细地阐述我的“密封类”观点。我想有一种方法可以展示我感兴趣的答案,那就是给我自己一个答案:)
意见:在c#中,默认情况下类应该是密封的
推理:
There's no doubt that inheritance is powerful. However, it has to be somewhat guided. If someone derives from a base class in a way which is completely unexpected, this can break the assumptions in the base implementation. Consider two methods in the base class, where one calls another - if these methods are both virtual, then that implementation detail has to be documented, otherwise someone could quite reasonably override the second method and expect a call to the first one to work. And of course, as soon as the implementation is documented, it can't be changed... so you lose flexibility.
C# took a step in the right direction (relative to Java) by making methods sealed by default. However, I believe a further step - making classes sealed by default - would have been even better. In particular, it's easy to override methods (or not explicitly seal existing virtual methods which you don't override) so that you end up with unexpected behaviour. This wouldn't actually stop you from doing anything you can currently do - it's just changing a default, not changing the available options. It would be a "safer" default though, just like the default access in C# is always "the most private visibility available at that point."
通过让人们明确表示他们希望人们能够从他们的类中派生,我们将鼓励他们更多地思考这个问题。这也可以帮助我解决我的懒惰问题——虽然我知道我应该密封几乎所有的类,但我很少真的记得这样做:(
对方观点:
我可以看到这样一种说法:可以相对安全地派生没有虚方法的类,而不需要额外的灵活性和通常需要的文档。目前我不确定如何应对这个问题,只能说我相信意外打开类的危害比意外密封类的危害更大。
单身人士并不邪恶
There is a place for singletons in the real world, and methods to get around them (i.e. monostate pattern) are simply singletons in disguise. For instance, a Logger is a perfect candidate for a singleton. Addtionally, so is a message pump. My current app uses distributed computing, and different objects need to be able to send appropriate messages. There should only be one message pump, and everyone should be able to access it. The alternative is passing an object to my message pump everywhere it might be needed and hoping that a new developer doesn't new one up without thinking and wonder why his messages are going nowhere. The uniqueness of the singleton is the most important part, not its availability. The singleton has its place in the world.