在@IllidanS4的回答基础上,我创建了一个模板类,允许传递预定义参数和类实例的几乎任何成员函数以供后期调用。
template<class RET, class... RArgs> class Callback_t {
public:
virtual RET call(RArgs&&... rargs) = 0;
};
template<class T, class RET, class... RArgs> class CallbackCalltimeArgs : public Callback_t<RET, RArgs...> {
public:
T * owner;
RET(T::*x)(RArgs...);
RET call(RArgs&&... rargs) {
return (*owner.*(x))(std::forward<RArgs>(rargs)...);
};
CallbackCalltimeArgs(T* t, RET(T::*x)(RArgs...)) : owner(t), x(x) {}
};
template<class T, class RET, class... Args> class CallbackCreattimeArgs : public Callback_t<RET> {
public:
T* owner;
RET(T::*x)(Args...);
RET call() {
return (*owner.*(x))(std::get<Args&&>(args)...);
};
std::tuple<Args&&...> args;
CallbackCreattimeArgs(T* t, RET(T::*x)(Args...), Args&&... args) : owner(t), x(x),
args(std::tuple<Args&&...>(std::forward<Args>(args)...)) {}
};
测试/示例:
class container {
public:
static void printFrom(container* c) { c->print(); };
container(int data) : data(data) {};
~container() {};
void print() { printf("%d\n", data); };
void printTo(FILE* f) { fprintf(f, "%d\n", data); };
void printWith(int arg) { printf("%d:%d\n", data, arg); };
private:
int data;
};
int main() {
container c1(1), c2(20);
CallbackCreattimeArgs<container, void> f1(&c1, &container::print);
Callback_t<void>* fp1 = &f1;
fp1->call();
CallbackCreattimeArgs<container, void, FILE*> f2(&c2, &container::printTo, stdout);
Callback_t<void>* fp2 = &f2;
fp2->call();
CallbackCalltimeArgs<container, void, int> f3(&c2, &container::printWith);
Callback_t<void, int>* fp3 = &f3;
fp3->call(15);
}
显然,这只有在给定的参数和所有者类仍然有效时才能起作用。就可读性而言...请原谅我。
编辑:通过使元组成为普通存储来删除不必要的malloc。为引用添加继承类型。添加在调用时提供所有参数的选项。现在正在处理两个问题...
编辑2:如承诺的那样,两者都可以。唯一的限制(我看到的)是预定义的参数必须在回调函数中的运行时提供的参数之前。感谢@Chipster在gcc兼容性方面的帮助。这在ubuntu上的gcc和Windows上的visual studio上工作。
#ifdef _WIN32
#define wintypename typename
#else
#define wintypename
#endif
template<class RET, class... RArgs> class Callback_t {
public:
virtual RET call(RArgs... rargs) = 0;
virtual ~Callback_t() = default;
};
template<class RET, class... RArgs> class CallbackFactory {
private:
template<class T, class... CArgs> class Callback : public Callback_t<RET, RArgs...> {
private:
T * owner;
RET(T::*x)(CArgs..., RArgs...);
std::tuple<CArgs...> cargs;
RET call(RArgs... rargs) {
return (*owner.*(x))(std::get<CArgs>(cargs)..., rargs...);
};
public:
Callback(T* t, RET(T::*x)(CArgs..., RArgs...), CArgs... pda);
~Callback() {};
};
public:
template<class U, class... CArgs> static Callback_t<RET, RArgs...>* make(U* owner, CArgs... cargs, RET(U::*func)(CArgs..., RArgs...));
};
template<class RET2, class... RArgs2> template<class T2, class... CArgs2> CallbackFactory<RET2, RArgs2...>::Callback<T2, CArgs2...>::Callback(T2* t, RET2(T2::*x)(CArgs2..., RArgs2...), CArgs2... pda) : x(x), owner(t), cargs(std::forward<CArgs2>(pda)...) {}
template<class RET, class... RArgs> template<class U, class... CArgs> Callback_t<RET, RArgs...>* CallbackFactory<RET, RArgs...>::make(U* owner, CArgs... cargs, RET(U::*func)(CArgs..., RArgs...)) {
return new wintypename CallbackFactory<RET, RArgs...>::Callback<U, CArgs...>(owner, func, std::forward<CArgs>(cargs)...);
}
编辑3:符合clang标准,更灵活的功能和示例。(从我的活动爱好项目中提取,我计划最终开源...)
#pragma once
#ifdef _WIN32
#define wintypename typename
#else
#define wintypename
#endif
namespace WITE {
template<class RET, class... RArgs> class Callback_t {
public:
virtual RET call(RArgs... rargs) const = 0;
virtual ~Callback_t() = default;
};
template<class RET, class... RArgs> class CallbackFactory {
private:
template<class T, class... CArgs> class Callback : public Callback_t<RET, RArgs...> {
private:
RET(T::*x)(CArgs..., RArgs...);
T * owner;
std::tuple<CArgs...> cargs;
public:
Callback(T* t, RET(T::*x)(CArgs..., RArgs...), CArgs... pda);
~Callback() {};
RET call(RArgs... rargs) const override {
return (*owner.*(x))(std::get<CArgs>(cargs)..., rargs...);
};
};
template<class... CArgs> class StaticCallback : public Callback_t<RET, RArgs...> {
private:
RET(*x)(CArgs..., RArgs...);
std::tuple<CArgs...> cargs;
public:
StaticCallback(RET(*x)(CArgs..., RArgs...), CArgs... pda);
~StaticCallback() {};
RET call(RArgs... rargs) const override {
return (*x)(std::get<CArgs>(cargs)..., rargs...);
};
};
public:
typedef Callback_t<RET, RArgs...>* callback_t;
template<class U, class... CArgs> static callback_t make(U* owner, CArgs... cargs, RET(U::*func)(CArgs..., RArgs...));
template<class... CArgs> static callback_t make(CArgs... cargs, RET(*func)(CArgs..., RArgs...));
};
template<class RET2, class... RArgs2> template<class T2, class... CArgs2>
CallbackFactory<RET2, RArgs2...>::Callback<T2, CArgs2...>::Callback(T2* t, RET2(T2::*x)(CArgs2..., RArgs2...), CArgs2... pda) :
x(x), owner(t), cargs(std::forward<CArgs2>(pda)...) {}
template<class RET2, class... RArgs2> template<class... CArgs2>
CallbackFactory<RET2, RArgs2...>::StaticCallback<CArgs2...>::StaticCallback(RET2(*x)(CArgs2..., RArgs2...), CArgs2... pda) :
x(x), cargs(std::forward<CArgs2>(pda)...) {}
template<class RET, class... RArgs> template<class U, class... CArgs> Callback_t<RET, RArgs...>*
CallbackFactory<RET, RArgs...>::make(U* owner, CArgs... cargs, RET(U::*func)(CArgs..., RArgs...)) {
return new wintypename CallbackFactory<RET, RArgs...>::Callback<U, CArgs...>(owner, func, std::forward<CArgs>(cargs)...);
};
template<class RET, class... RArgs> template<class... CArgs> Callback_t<RET, RArgs...>*
CallbackFactory<RET, RArgs...>::make(CArgs... cargs, RET(*func)(CArgs..., RArgs...)) {
return new wintypename CallbackFactory<RET, RArgs...>::StaticCallback<CArgs...>(func, std::forward<CArgs>(cargs)...);
};
#define typedefCB(name, ...) typedef WITE::CallbackFactory<__VA_ARGS__> name## _F; typedef typename name## _F::callback_t name ;
typedefCB(rawDataSource, int, void*, size_t)
};
class Integer {
public:
typedefCB(oneInOneOut, int, int);
typedefCB(twoInOneOut, int, int, int);
int value;
Integer(int v) : value(v) {};
int plus(int o) {
return value + o;
};
int plus(int a, int b, int c) {
return value + a + b + c;
};
static int simpleSum(int a, int b) {
return a + b;
};
};
int main(int argc, char** argv) {
Integer::twoInOneOut sumOfTwo = Integer::twoInOneOut_F::make(&Integer::simpleSum);
std::cout << sumOfTwo->call(5, 6) << std::endl;
Integer seven(7);
Integer::oneInOneOut sevenPlus = Integer::oneInOneOut_F::make<Integer>(&seven, &Integer::plus);
std::cout << sevenPlus->call(12) << std::endl;
Integer::twoInOneOut seventeenPlus = Integer::twoInOneOut_F::make<Integer, int>(&seven, 10, &Integer::plus);
std::cout << seventeenPlus->call(52, 48) << std::endl;
}
在撰写本文时,我遇到了
libstdc++已知的错误#71096,当在回调构建时给出>1个参数时,会破坏
std::get
。这个错误已经在gcc 11中标记为修复,但不幸的是,它目前还没有进入ubuntu仓库(apt显示我已经更新到9.3.0)。