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13 - handmade any class.cpp
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13 - handmade any class.cpp
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#include <memory>
#include <iostream>
template <typename Concept>
struct any : Concept {
template <typename T>
void operator=(T t) { o = std::make_unique<object<T>>(t); }
};
#define MEMBER_FUNCTION(x, y) \
template <typename T> \
struct x; \
template <typename ReturnType, typename... Args> \
struct x<ReturnType(Args...)> { \
ReturnType y(Args... args) { \
return o->invoke(args...); \
} \
protected: \
struct object_base { \
virtual ~object_base() = default; \
virtual ReturnType invoke(Args...) = 0; \
}; \
template <class T> \
struct object : object_base { \
object(T t) : t(t) {} \
ReturnType invoke(Args... args) override { return t.y(args...); } \
private: \
T t; \
}; \
std::unique_ptr<object_base> o; \
};
struct TCPConnection {
void send(const char *s) { std::cout << "TCP: " << s << '\n'; }
};
struct UDPConnection {
void send(const char *s) { std::cout << "UDP: " << s << '\n'; }
};
MEMBER_FUNCTION(has_send, send)
using Connection = any<has_send<void(const char*)>>;
int main(int argc, char *argv[]) {
Connection c;
c = TCPConnection();
c.send("Hello");
c = UDPConnection();
c.send("Hello");
}