是否将 null 传递给可接受的方法 [英] Is passing null in to a method acceptable

问题描述

Null 对我来说是一种奇怪的数据类型，似乎永远使用它是错误的，也许是我作为初学者经常遇到的空指针错误，现在让我将任何 null 实例与某种邪恶相关联！

Null is an odd data type for me, it seems as though it is wrong to ever use, maybe its the null pointer errors i got so often as a beginner that now have me associating any instance of null to some kind of evil!

无论如何我的问题是

在某些情况下可以使用 null 作为参数吗?例如，一个方法可能需要a和b来完成一个任务，但在某些情况下它可能只需要a.在那些奇怪的实例中为 b 解析 null 是否可以并检查 if(b==null) 那么我们知道它叫什么?

in some cases is it ok to use null as a parameter? for example, a method may need a and b to do a task, but in some cases it may only need a. Is parsing in null ok for b in those odd instances and checking if(b==null) then we know what called it?

或者我在这里的标记方式?

Or am i way of the mark here?

我必须承认，让我想知道这是否可以接受的是，所讨论的方法可能会过载，但在整个方法中可能会有 5 或 6 行的差异.这让我担心代码重复.

i must admit, what got me wondering whether this was acceptable was, the method in question could be overlaoded, but it would have a difference of possibly 5 or 6 lines out of the whole method. This made me worried about code duplication.

推荐答案

将 null 传递给方法绝对没问题.但是，如果您有可能不需要传递变量的 csae，请考虑 重载.

It is absolutely fine to pass null to methods. However, if you have a csae where you might not need to pass a variable, consider overloading.

我个人不使用可选参数 - 由于方法作为合同的问题，有很多关于这个主题的讨论，其中不在此问题的范围内.

I personally would not use optional parameters - there are many discussions on this very subject because of the issue with the method as Contract which is outside the scope of this question.

正确的做法不是重复代码而是让重载相互调用:

Correct way to do it is not to duplicate code but let overloads call each other:

public void Foo(A a)
{
    Foo(a, null);
}
public void Foo(A a, B b)
{
        // .......
}

这将告诉客户端此代码:

This will tell client of this code:

• 只能使用 A 调用方法
• 您可以使用 A 和 B 调用方法

如果我只有第二种方法，客户端将不知道是否可以传递null.

If I have only the second method, the client would not know if it is OK to pass null.

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