使用同一个类中的函数在类内部创建线程 [英] Create thread inside class with function from same class

问题描述

我希望能够定义一个包含一些数据成员的类，以及一个可以访问那些将是私有的数据成员的函数.

I want to be able to define a class with some data members, and a function which has access to those data members, which are to be private.

然后，我想要一个公共函数，该函数创建一些线程，这些线程对类的数据成员进行操作.我在编译代码时遇到了麻烦.

I then want a public function, which creates some threads, which operate on the data members of the class. I am having some trouble getting my code to compile.

不必担心互斥或数据保护，这不会成为问题，因为这只是一些测试示例代码.

Don't worry about mutex or data protection, this isn't going to be a problem, since this is just some example code for testing.

class foo {
    public:
    void make_foo_func_threads();

    private:
    void foo_func();

    char private_data;
    std::vector<std::thread> some_threads;
}

void foo::foo_func() {
    while(1) {
        private_data = 'A';
    }
}

void foo::make_foo_func_thread() {
    for(...) some_threads.push_back(std::thread(foo_func));
    for(...) some_threads.join();
}

编译器给我错误:

'没有匹配调用std :: thread :: thread()'

'no matching call to std::thread::thread()'

显然，没有已知的参数1从<unresolved overloaded function type>转换为void (foo::*&&)'的转换.

Apparently there is 'no known conversion for argument 1 from <unresolved overloaded function type> to void (foo::*&&)'.

Erm，是的，除了编译器难以理解如何解析foo_func之外，我不知道这意味着什么.

Erm, yeah, I have no idea what that means apart from the compiler is having trouble understanding how to resolve foo_func - I think.

我如何帮助编译器理解我要做什么，所以它不会再给我带来任何错误.毫无疑问，我编写的代码是不合法的，如果是这样的话，有人可以向我解释为什么.谢谢！

How can I help the compiler understand what I am trying to do, so it won't bother me with any more errors. No doubt the code I have written is not legal, and if that is the case could someone explain why that is the case to me. Thanks!

推荐答案

foo_func是(非static)成员函数，它需要foo的实例可以在其上进行操作.该实例必须提供给线程构造函数.如果您参考 std :: thread :: thread 参考页，解释了在新线程中执行什么代码.相关的一点是，它引用f是成员函数的指针:

foo_func is a (non-static) member function, and it needs an instance of foo on which to operate. This instance must be provided to the thread constructor. If you refer to the std::thread::thread reference page it explains what code is executed in the new thread. The relevant point is that which refers to f being a pointer to member function:

• 如果f是指向类T的成员函数的指针，则将其调用.返回值将被忽略.有效地，执行以下代码:
  • (t1.*f)(t2, ..., tN)，如果t1的类型是T，则引用T或引用从T派生的类型.
  • ((*t1).*f)(t2, ..., tN)否则.

• If f is pointer to a member function of class T, then it is called. The return value is ignored. Effectively, the following code is executed:
  • (t1.*f)(t2, ..., tN) if the type of t1 is either T, reference to T or reference to type derived from T.
  • ((*t1).*f)(t2, ..., tN) otherwise.

因此很明显该实例是必需的.

so it is clear that the instance is required.

更改为:

for(...) some_threads.push_back(std::thread(&foo::foo_func, this));

简单示例:

#include <iostream>
#include <thread>
#include <vector>

class foo
{
public:
    void make_foo_func_threads()
    {
        for (int i = 0; i < 5; ++i)
            some_threads.push_back(std::thread(&foo::foo_func, this));
        for (auto& t: some_threads) t.join();
    }

private:
    void foo_func() { std::cout << "Hello\n"; }
    std::vector<std::thread> some_threads;
};

int main()
{
    foo f;
    f.make_foo_func_threads();
}

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