如何在一个类的构造函数中生成一个随机数在C＃ [英] How to generate a random number in the constructor of a class in C#

问题描述

我知道，在C＃中的类的构造函数中调用一个方法并不是一个好习惯，但我坚持一些奇怪的东西。我的问题是，当我创建一个类的对象，我需要在我的对象中分配一个字段随机数。

I know that it is not a good practice to call a method in the constructor of a class in C# but I stuck on something strange. My problem is that when I create an object of my class I need to assign a field in my object with a random number.

例如

class RandomNumberHandler
    {
        private int randomNumber;
        public RandomNumberHandler()
        {
            this.randomNumber = GenerateRandomNumber();
        }

        private int GenerateRandomNumber()
        {
            return (new Random()).Next(3000) + 1000;
        }
    }

在我的例子中，我需要一个四位数字。我想在类中创建的随机数，其中我创建的对象，并将其作为参数传递给构造函数，但在其他类中生成一个随机数似乎不是一个很好的主意，因为我试图实现强的内聚为我的课。我在这里做一个高质量的代码课程在我的大学，我寻找最好的方法。欢迎任何想法如何做到这一点：）

In my case I need a four digit number. I thought of generating the random number in the class where I am creating the object and passing it as a parameter to the constructor but generating a random number in the other class does not seem a very good idea either because I am trying to achieve strong cohesion for my classes. I am doing this for a "High quality code" course in my university and I am looking for the best approach. Any ideas how to do this are welcome :)

推荐答案

首先：调用非虚拟构造函数中的方法。你在哪里读到那里？ （注意：调用 方法可能是一个问题;它不是一个自动的no-no，但你需要非常仔细地观察你在做什么。）

First off: there is nothing wrong with calling non-virtual methods in the constructor. Where did you read that there was? (Note: calling virtual methods can be a problem; it is not an automatic no-no, but you need to watch what you are doing very carefully).

另外，每次 GenerateRandomNumber 随机 c $ c>被调用。您可以将 Random 实例提取到字段以修复：

As an aside, it seems wasteful to generate a new Random instance every time GenerateRandomNumber is called. You can extract the Random instance to a field to fix that:

class RandomNumberHandler
{
    private readonly Random random = new Random();
    private int randomNumber;

    public RandomNumberHandler()
    {
        this.randomNumber = GenerateRandomNumber();
    }

    private int GenerateRandomNumber()
    {
        return this.random.Next(3000) + 1000;
    }
}

但这又引出了另一个问题：if GenerateRandomNumber 在每个实例的生命周期（在构造函数中）只调用一次，那么创建一个新的 Random 每个对象。因此，下一个逻辑步骤是使 random 为 static 。这意味着 GenerateRandomNumber 也可以变成 static （确实，它必须）：

But this raises another question: if GenerateRandomNumber is only called once in each instance's lifetime (in the constructor), then it doesn't make sense to create a new Random for each object. So the next logical step is to make random be static. This means that GenerateRandomNumber can also become static (and indeed, it has to):

class RandomNumberHandler
{
    private static readonly Random Random = new Random();
    private int randomNumber;

    public RandomNumberHandler()
    {
        this.randomNumber = GenerateRandomNumber();
    }

    private static int GenerateRandomNumber()
    {
        return Random.Next(3000) + 1000;
    }
}

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