随机数同类初始化 [英] Random Number In-Class Initialisation

问题描述

我目前正在创建一个类，我希望每次创建对象时，使用随机数来初始化其中一个私有成员。以下代码不会产生问题：

I am currently making a class for which I'd like one of the private members to be initialised with a random number each time the object is created. The following code causes no problem:

private:
    unsigned random = rand() % 10;

然而，我想使用C ++ 11随机引擎和发行版。我想能够按照下面的代码行，它不会编译，但会提供一个大致的想法，我想做的事情：

I would, however, like to use the C++11 random engines and distributions to do this. I would like to be able to do something along the lines of the following code, which will not compile but will give a general idea of what I'm trying to do:

private:
unsigned random = distribution(mersenne_generator(seed));

static std::random_device seed_generator;
static unsigned seed = seed_generator(); //So that it's not a new seed each time.
static std::mt19937 mersenne_generator;
static std::uniform_int_distribution<unsigned> distribution(0, 10);

此代码将无法编译，因为我想在类中定义一些静态成员。我不知道在哪里定义它们，但是。我可以创建一个成员函数初始化一切，但然后我必须在main中运行它，我不想。我想只是整理出所有的随机定义在类中，所以当我在main中创建一个对象，它将隐式创建的随机数。任何建议？

This code won't compile because I'm trying to define some of the static members in the class. I'm not sure where to define them, however. I could create a member function that initialises everything, but then I would have to run it in main, which I don't want to. I would like to just sort out all the random definitions in class so that when I create an object in main, it will create the random number implicitly. Any suggestions?

推荐答案

您需要在类定义之外定义静态数据成员。例如，这将工作：

You need to define the static data members outside the class definition. For instance, this will work:

struct foo
{
private:
    unsigned random = distribution(mersenne_generator);    
    static std::random_device seed_generator;
    static unsigned seed;
    static std::mt19937 mersenne_generator;
    static std::uniform_int_distribution<unsigned> distribution;
};

std::random_device foo::seed_generator;
unsigned foo::seed = seed_generator();
std::uniform_int_distribution<unsigned> foo::distribution(0, 10);
std::mt19937 foo::mersenne_generator(foo::seed);

静态数据成员的定义应放在.cpp文件中，否则运行风险违反了一个定义规则。

The definitions for the static data members should be placed in a .cpp file, else you run the risk of violating the one definition rule.

实例

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