【发布时间】：2018-04-03 00:01:20
【问题描述】：
我正在尝试在 C++ 中实现 Signal 模板。
这是我目前所拥有的：
Main.cpp:
//Developed by Trofimov Yaroslav on 02.04.18
#include <iostream>
#include "Signal.h"
void f1() {
std::cout << "here in f1" << std::endl;
}
void f2() {
std::cout << "F2 F2 F2" << std::endl;
}
typedef void (* VoidResultDelegate)();
int main(void) {
Signal<VoidResultDelegate> signalVoid;
signalVoid.addListener(f1);
signalVoid.addListener(f1);
signalVoid.invoke();
signalVoid.removeListener(f2);
signalVoid.invoke();
return 0;
}
Signal.h:
//Developed by Trofimov Yaroslav on 02.04.18
#ifndef _SIGNAL_H_TROFIMOV_
#define _SIGNAL_H_TROFIMOV_
#include "LinkedList.h"
template<typename FunctionType>
class Signal {
LinkedList<FunctionType> _delegates;
public:
Signal<FunctionType>(void)
: _delegates(LinkedList<FunctionType>()) {
}
~Signal<FunctionType>(void) {
}
void addListener(const FunctionType& delegated) {
_delegates.add(delegated);
}
void removeListener(const FunctionType& delegated) {
_delegates.remove(delegated);
}
void invoke() {
_delegates.startIteration();
while(_delegates.hasNext()) {
_delegates.next()();
}
}
};
#endif
LinkedList.h:
//Developed by Trofimov Yaroslav on 30.03.2018
#ifndef _LINKED_LIST_H_TROFIMOV_
#define _LINKED_LIST_H_TROFIMOV_
#include <string>
#include <iostream>
#include <typeinfo>
template<typename T>
class LinkedList {
template<typename T>
struct Node {
T _data;
Node* _next;
Node()
: _next(0){}
~Node<T>() {
if(_next) {
delete _next; _next = 0;
}
}
};
Node<T>* _head;
Node<T>* _tail;
Node<T>* _iterator;
public:
LinkedList<T>()
: _head(0), _tail(0), _iterator(0) {
};
~LinkedList<T>() {
delete _head; _head = 0;
}
void add(const T& element) {
if(!_head) {
_head = new Node<T>;
_head->_data = element;
_tail = _head;
return;
}
Node<T>* newNode = new Node<T>;
newNode->_data = element;
_tail->_next = newNode;
_tail = newNode;
return;
}
void remove(const T& element) {
if(!_head) {
return;
}
if(_head->_data == element) {
_head = _head->_next;
return;
}
Node<T>* previous = _head;
Node<T>* current = _head->_next;
while(current) {
if(current->_data == element) {
previous->_next = current->_next;
return;
}
previous = current;
current = current->_next;
}
}
void startIteration() {
_iterator = _head;
}
bool hasNext() {
return (_iterator)?true:false;
}
T& next() {
T& res = _iterator->_data;
_iterator = _iterator->_next;
return res;
}
};
#endif
所以，我想补充的是一种通用的参数传递方式。假设现在我有typedef void (* VoidResultDelegate)(int i); 而不是typedef void (* VoidResultDelegate)();，这意味着我希望int 参数以某种方式出现在Signal::invoke 方法参数列表中，并以_delegates.next()(); 的方式传递到这里_delegates.next()(i); 或类似的东西。
在 C++ 中是否有可能？
我正在考虑将另一个typename 参数传递给Signal，它表示Signal::invoke 接受的参数类型，并在调用_delegates.next()(); 中传递给链表中的元素。但是这种方法的问题是我无法控制参数的数量（它将只有一个参数）。并且没有人（当然我指的是编译器）强制我将正确的参数作为typename 传递给Signal 模板。在上面的示例中，我可以通过 bool typename 而不是 int 并且在出现错误之前没有人会注意到它。
这里是回答后的更新版本：
Main.cpp：
//Developed by Trofimov Yaroslav on 02.04.18
#include <iostream>
#include "Signal.h"
void f1(int i) {
std::cout << "here in f1" << std::endl;
}
void f2(int i) {
std::cout << "F2 F2 F2" << std::endl;
}
typedef void (* VoidResultDelegate)(int i);
int main(void) {
Signal<VoidResultDelegate, int> signalVoid;
signalVoid.addListener(f1);
signalVoid.addListener(f2);
signalVoid.invoke(-1);
signalVoid.removeListener(f1);
signalVoid.invoke(-1);
return 0;
}
Signal.h：
//Developed by Trofimov Yaroslav on 02.04.18
#ifndef _SIGNAL_H_TROFIMOV_
#define _SIGNAL_H_TROFIMOV_
#include "LinkedList.h"
template<typename FunctionType, typename... Args>
class Signal {
LinkedList<FunctionType> _delegates;
public:
Signal<FunctionType, parameter>(void)
: _delegates(LinkedList<FunctionType>()) {
}
~Signal<FunctionType, parameter>(void) {
}
void addListener(const FunctionType& delegated) {
_delegates.add(delegated);
}
void removeListener(const FunctionType& delegated) {
_delegates.remove(delegated);
}
void invoke(Args&& ... args) {
_delegates.startIteration();
while(_delegates.hasNext()) {
(_delegates.next())(std::forward<Args>(args)...);
}
}
};
#endif
LinkedList.h:
//Developed by Trofimov Yaroslav on 30.03.2018
#ifndef _LINKED_LIST_H_TROFIMOV_
#define _LINKED_LIST_H_TROFIMOV_
#include <string>
#include <iostream>
#include <typeinfo>
template<typename T>
class LinkedList {
template<typename T>
struct Node {
T _data;
Node* _next;
Node()
: _next(0){}
~Node<T>() {
if(_next) {
delete _next; _next = 0;
}
}
};
Node<T>* _head, _tail, _iterator;
public:
LinkedList<T>()
: _head(0), _tail(0), _iterator(0) {
};
~LinkedList<T>() {
delete _head; _head = 0;
}
void add(const T& element) {
if(!_head) {
_head = new Node<T>;
_head->_data = element;
_tail = _head;
return;
}
Node<T>* newNode = new Node<T>;
newNode->_data = element;
_tail->_next = newNode;
_tail = newNode;
return;
}
void remove(const T& element) {
if(!_head) {
return;
}
if(_head->_data == element) {
_head = _head->_next;
return;
}
Node<T>* previous = _head;
Node<T>* current = _head->_next;
while(current) {
if(current->_data == element) {
previous->_next = current->_next;
return;
}
previous = current;
current = current->_next;
}
}
void startIteration() {
_iterator = _head;
}
bool hasNext() {
return (_iterator)?true:false;
}
T& next() {
T& res = _iterator->_data;
_iterator = _iterator->_next;
return res;
}
};
#endif
【问题讨论】：
标签： c++ function types parameters signals