合格名单<类>作为参数，C#，使用“ref"；关键词 [英] Passing List<Class> as argument, C#, using "ref" keyword

问题描述

朋友们！

所以我一直在写一个简单的程序.基本上，我有一个类(3 个字符串，1 个整数，一些方法).我正在从文本文件初始化此类的对象的值.我为此使用列表.问题是初始化是一个单独的函数.我在此函数中声明并初始化了 List BOTH.但是，我可能在其他函数中需要它，包括Program.Main".

So I have been writing a simple program. Basically, I have a class (3 strings, 1 int, some methods). I am initializing the values of objects of this class from a text file. I am using List for this. The problem is that initialization is a separate function. I had List BOTH declared AND initialized in this function. However, I might need it in other functions, including "Program.Main".

我应该创建一个全局"类并放置一个公共列表<类> ?我决定现在就在我的 Program.Main 函数中声明它.但是，我不确定 List 是按值传递还是按引用传递.我在网上找到了一个页面，建议使用 ref 关键字.现在我有:

Should I make a "Global" class and put make a public List< Class > ? I decided to just declare it in my Program.Main function as of now. However, I am not sure, if a List is passed by value or by reference. I found a page on the Web, which suggests using ref keyword. Now I have:

public Class FooClass
{...}

class Program
{
    static void Main(string[] args)
    {
      List<FooClass> fooDB = new List<FooClass>;
      initFromFile(ref fooDB);
    }

    private static initFromFile(ref List<FooClass> fooDB)
    {
       using (StreamReader ... )
       {
          while( ... )
          {
             ...
             fooDB.Add(new FooClass(args))
          }
       }
     }//initFromFile

}//Program

我应该继续这样工作吗?或者有什么重要的建议?也许ref"根本不是一个好习惯?

Should I keep on working like this? Or are there any crucial suggestions? Maybe "ref" isn't a good practice at all?

TLDR:我应该制作一个全局 List 还是将其作为参考或其他方式传递(建议).如果通过引用传递，那么我应该使用 ref 关键字还是有其他方法?

TLDR: Should i make a global List or pass it as a reference or another way(suggest). If passing by reference, then should I use a ref keyword or is there another way?

提前致谢，

~~~hlrmn

推荐答案

你的程序结构很好，除了不需要使用ref.List 是一个引用类型，意味着传递给函数的值实际上是一个引用(C中的指针"/C++ 术语)到 List 实例.因此，当函数返回时，对方法中列表的任何修改都将可用.

The way your program is structured is just fine, except there's no need toi use ref. List<T> is a reference type, meaning that the value that is passed to the function is actually a reference ("pointer" in C/C++ terms) to a List<T> instance. So any modifications to the list within the method will be available when the function returns.

使用 ref 的唯一原因是，如果您想将 fooDB 指向一个新的 实例:

The only reason you would use ref is if you wanted to point fooDB to a new instance:

private static initFromFile(ref List<FooClass> fooDB)
{

  fooDB = new List<FooClass>; // if the parameter was not passed by reference 
                               // this instance would not be used by the caller.
  using (StreamReader ... ){
  while( ... )
  {
    ...
    fooDB.Add(new FooClass(args))
  }}
}//initFromFile

编辑

仔细阅读你问题的第一部分，似乎 fooDB 应该是一个被初始化的 类成员:

Reading the first part of your question more closely, it seems like fooDB should possibly be a class member that is initialized:

class Program
{
    private static List<FooClass> fooDB;

    static void Main(string[] args)
    {
      initFromFile();
      foreach(FooClass f in fooDB)
      {
          // do something
      }
    }

    private static initFromFile()
    {
       fooDB = new List<FooClass>();
       using (StreamReader ... )
       {
          while( ... )
          {
             ...
             fooDB.Add(new FooClass(args))
          }
       }
     }//initFromFile

}//Program

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