使用静态函数变量vs类变量来存储一些状态 [英] Using static function variable vs class variable to store some state

问题描述

假设我有这样的功能：

  void processElement（）{
 doSomething（someArray [lastProcessedElement + 1]）;事情是，每次这个函数调用时，我需要到存储库中。最后一个元素，我叫doSomething。所以在这里我有两个选择：
 
 
 
 
 
 
我可以创建一个私有类变量名为lastProcessedElement，叫做。这种方法似乎最常见。所以代码可以这样：
  class Foo {
 int lastProcessedElement = 0; 
 
 public：
 void processElement（）{
 doSomething（someArray [++ lastProcessedElement]）; 
} 
} 
  
 
 
 
 
作为第二个选项，函数中的静态变量并且每次都增加：
  //类在这里不重要，因此函数是：
 void processElement（）{
 static int lastProcessedElement = 0; 
 doSomething（someArray [++ lastProcessedElement]）; 
} 
  
 
 
 
 
 
 
有点复杂，我不想要。 
 
 
 
我知道第二个解决方案只有在该类只有一个实例时才有效。
 
 
 
那么使用静态变量方法是一个很好的解决方案？并且有多任务在线解决方案多实例类？ （可以有一个解决方案，这个特定的数组元素索引的东西，但我只是这样，我说的是存储一些值的函数的下一次调用）
解决方案
您已经知道为什么函数范围的静态是一个坏主意：
 
 
 
 
 
这是一个不好的设计限制。
 
 
 
只需将状态保持为常规类成员变量。
 
Lets say I have function like this:
void processElement() {
    doSomething(someArray[lastProcessedElement + 1]);
}
The thing is, every time this function called, I need to the store the last element that I called doSomething on. So in here I have two choices:


I can create a private class variable named lastProcessedElement and increment it's value every time that function is called. This approach seems most common. So the code can be something like this:
class Foo {
    int lastProcessedElement = 0;     

    public:  
    void processElement() {
        doSomething(someArray[++lastProcessedElement]);
    }
}

As second option, I can create a static variable in function and increment it every time:
// Class is not important here, so the function is:
void processElement() {
    static int lastProcessedElement = 0;
    doSomething(someArray[++lastProcessedElement]);
}



The first solution adds a little bit complexity which I don't want. I like to keep things in-place.

I know the second solution only works if that class have only one instance.

So using static variable method is a good solution? And is there any in-line solution to multi-instance class? (There can be a solution to this particular array element index thing, but I just made that up, I'm talking about storing some value for the next call of the function)
解决方案
You already figured out why the function-scoped static is a bad idea:

  
only works if that class have only one instance
That's a bad design limitation.

Just keep the state as a regular class member variable.

                        
这篇关于使用静态函数变量vs类变量来存储一些状态的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！