I have this code that attempts perfect forwarding of template parameters pack into std::function
via intermediate class:
#include <functional>
#include <vector>
#include <algorithm>
#include <iterator>
#include <memory>
#include <iostream>
template <typename ...Arguments>
class CSignal
{
public:
typedef std::function<void (Arguments...)> SignalFunction;
public:
void connect(const SignalFunction& target)
{
m_connections.emplace_back(std::make_shared<SignalFunction>(target));
}
template <typename ...ActualArguments>
void invoke(ActualArguments&&... args) const
{
for (auto& connection: m_connections)
if (connection)
(*connection)(std::forward<ActualArguments>(args)...);
}
private:
std::vector<std::shared_ptr<SignalFunction>> m_connections;
};
struct A
{
void f() {std::cout << __FUNCTION__ << "\n";}
};
void test(std::shared_ptr<A> ptr)
{
if (ptr)
ptr->f();
}
int main()
{
CSignal<std::shared_ptr<A>> signal;
signal.connect(test);
signal.connect(test);
signal.invoke(std::make_shared<A>());
return 0;
}
Problem: test
is called twice, and the second time it's called its parameter is empty
pointer. Why?
If I remove std::forward
the issue disappears, but that's not what I want.
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