你怎么用，可以是多种类型的变量工作？ [英] How do you work with a variable that can be of multiple types?

问题描述

我经常使用对象链接到他们的父母：

I frequently link objects to their parents using:

 Video parent;

有时候，我有对象可以是不同的对象类型的孩子，所以做我：

Sometimes I have objects that can be children of different object types, so do I:

 int parentType;
 Video parentVideo; // if parent == VIDEO then this will be used
 Audio parentAudio; // if parent == AUDIO then this will be used

有没有更好的办法？
我如何与可以是不同类型的实例变量工作

Is there a better way? How do I work with a variable that can be an instance of different types?

编辑：当然，如果视频和从相同的基类（如媒体），我能做到这一点音频继承：

Of course, if Video and Audio inherit from the same baseclass (eg. Media) I could do this:

 Media parent;

但是，如果家长不从同一个基类继承？

But what if the parents do not inherit from the same baseclass?

推荐答案

我假设你的问题的类型进行密封。在这种情况下，我只想用对象父，并使用为的出路。 （使用为可以拥有比检查一个标志一个更高的性能影响，但......不是在任何一个问题我已经做了，它也可以在一个空值很好地被使用门卫）

I am assuming that the types in your question are sealed. In which case I would just use object parent and use as on the way out. (Using as can have a higher performance impact than checking a flag, but... not a concern in anything I have done and it can also be nicely used in a null-guard.)

Video video = null;
if ((video = parent as Video) != null) {
  // know we have a (non-null) Video object here, yay!
} else if (...) {
  // maybe there is the Audio here
}

以上实际上只是在一个不受约束的识别联合编写一次性-模式匹配的一个愚蠢的C＃的方式（对象是在C＃中所有其他类型的工会： - ）

The above is actually just a silly C# way of writing a one-off-pattern-match on an unconstrained discriminated union (object is the union of every other type in C# :-)

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