将任何具有任意数量参数的类成员函数传递给类外的函数

Question

Remy发布了一个很好的解决方案，可以将任何具有任意数量参数的函数传递给std::thread。我想知道如何将它用于类成员函数。

#include <iostream>
#include <thread>
#include <mutex>
#define __PRETTY_FUNCTION__ __FUNCSIG__
std::mutex my_mutex;
template<class Function, class... Args>
void runFunctionInThread(Function f, Args&&... args) {
// Beside starting a thread, this function performs other 
// task using the function and its arguments.
std::thread t(f, std::forward<Args>(args)...);
t.detach();
}
class MyClass
{
public:
MyClass() {};
void myFunc1() { std::unique_lock<std::mutex> lock(my_mutex); std::cout << __PRETTY_FUNCTION__ << "n"; }
void myFunc2(int value) { std::unique_lock<std::mutex> lock(my_mutex); std::cout << __PRETTY_FUNCTION__ << "value is " << value << "n"; }
void myFunc3(int value1, int value2) { std::unique_lock<std::mutex> lock(my_mutex); std::cout << __PRETTY_FUNCTION__ << "value1+value2 is " << value1 + value2 << "n"; }
void manager() {
void (MyClass::*f1)() = &MyClass::myFunc1;
void (MyClass::*f2)(int) = &MyClass::myFunc2;
void (MyClass::*f3)(int,int) = &MyClass::myFunc3;
runFunctionInThread(f1);
runFunctionInThread(f2, 2);
runFunctionInThread(f3, 3, 3);
}
};
void isolatedFunc1() { std::unique_lock<std::mutex> lock(my_mutex); std::cout << __PRETTY_FUNCTION__ << "n"; }
void isolatedFunc2(int value) { std::unique_lock<std::mutex> lock(my_mutex); std::cout << __PRETTY_FUNCTION__ << " value is " << value << "n"; }
void isolatedFunc3(int value1, int value2) { std::unique_lock<std::mutex> lock(my_mutex); std::cout << __PRETTY_FUNCTION__ << " value1+value2 is " << value1 + value2 << "n"; }
int main()
{
runFunctionInThread(&isolatedFunc1); // Works flawlessly
runFunctionInThread(&isolatedFunc2, 2); // Works flawlessly
runFunctionInThread(&isolatedFunc3, 3, 3); // Works flawlessly
MyClass m;
m.manager();
}

Answer 1

如果要调用成员函数，还需要将对象传递给std::thread:

void manager() {
//...
runFunctionInThread(f1, this);
runFunctionInThread(f2, this, 2);
runFunctionInThread(f3, this, 3, 3);
}

注：我注意到你把线解开了。然后，您需要手动确保它们在程序运行之前已经结束，或者如果它们仍在运行，您将在程序退出时遇到意外。

通常更容易将正在运行的线程保存在容器中(如std::list<std::thread>(，稍后再将其保存在join()中。在C++20中，当容器被破坏时，您甚至可以将它们自动连接为std::list<std::jthread>。