定义相互依赖的类的c++宏
C++ macro defining classes dependent on each other
我试图编写宏，定义两个紧密连接的类一次，但我不能。下面是我的代码:
#ifndef SIGNALS_HPP
#define SIGNALS_HPP
#include <unordered_set>
#include <cstdio>
/**
* Macro defines pair of classes, sender and receiver. When one of them is destroyed,
* all it's connections are dully unconnected.
*
* EXAMPLE:
*
* signal(SomeEvent, some_event_occured)
*
* EXPANDS TO:
*
* class SomeEventReceiver {
* protected:
* virtual void on_some_event_occured() {}
* }
*
* class SomeEventSender {
* public:
* void connect_some_event_occured(SomeEventReceiver & listener); // registers listener
* void unconnect_some_event_occured(SomeEventReceiver & listener); // forgets listener
*
* protected:
* void send_some_event_occured(); // notifies all listeners
* }
*/
#define signal(signal_name, slot_name)
class signal_name##Sender;
class signal_name##Receiver
{
friend class signal_name##Sender;
std::unordered_set<signal_name##Sender*> senders;
protected:
virtual void on_##slot_name() {}
public:
virtual ~signal_name##Receiver();
};
class signal_name##Sender
{
friend class signal_name##Receiver;
std::unordered_set<signal_name##Receiver*> listeners;
public:
virtual ~signal_name##Sender()
{
for (auto i : listeners)
i->senders.erase(this);
listeners.clear();
}
void connect_##slot_name(signal_name##Receiver & listener)
{
listeners.insert(&listener);
listener.senders.insert(this);
}
void unconnect_##slot_name(signal_name##Receiver & listener)
{
listeners.erase(&listener);
listener.senders.erase(this);
}
protected:
void send_##slot_name()
{
for (auto i : listeners)
i->on_##slot_name();
}
};
/* // <-------------- THE LAST SECTION
signal_name##Receiver::~signal_name##Receiver()
{
for (auto i : senders)
i->listeners.erase(this);
senders.clear();
}//*/
#endif // SIGNALS_HPP
1)为什么最后一部分被注释了?我认为所有的虚方法必须要么定义或纯?
2)这个宏在另一个头文件中使用。当最后一部分没有注释时，我收到了很多"多重定义"错误。我相信我知道为什么它不起作用:最后一节算作定义，不应该在标题。但是我如何实现这样的宏呢?或者如果我错了，真正的问题是什么?
快速用法示例:
#ifndef SOME_HPP
#define SOME_HPP
signal(AA, aa)
class X : public AASender {
};
#endif
如果在一些。cpp文件中包含这样的内容(可能是间接的)，它会得到以下错误:"typeinfo for AAReceiver', first defined here, In function ~new_allocator"的多重定义:"。"typeinfo" varies to destructor and类型名称和虚表。接收方有时会变成发送方。
如果一个人真的喜欢阅读，那就有真正的错误:
army.o: In function `~BattleEndaaaaaaaReceiver':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `BattleEndaaaaaaaReceiver::~BattleEndaaaaaaaReceiver()'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
army.o: In function `~new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `BattleEndaaaaaaaReceiver::~BattleEndaaaaaaaReceiver()'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
army.o: In function `~new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `BattleEndaaaaaaaReceiver::~BattleEndaaaaaaaReceiver()'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
army.o: In function `std::__detail::_Hashtable_alloc<std::allocator<std::__detail::_Hash_node<BattleEndaaaaaaaSender*, false> > >::_M_deallocate_nodes(std::__detail::_Hash_node<BattleEndaaaaaaaSender*, false>*)':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `typeinfo for BattleEndaaaaaaaReceiver'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
army.o: In function `~new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `typeinfo name for BattleEndaaaaaaaReceiver'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
army.o: In function `~new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `vtable for BattleEndaaaaaaaReceiver'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
game.o: In function `~BattleEndaaaaaaaReceiver':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `BattleEndaaaaaaaReceiver::~BattleEndaaaaaaaReceiver()'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
game.o: In function `new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `BattleEndaaaaaaaReceiver::~BattleEndaaaaaaaReceiver()'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
game.o: In function `new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `BattleEndaaaaaaaReceiver::~BattleEndaaaaaaaReceiver()'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
game.o: In function `vector':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `typeinfo for BattleEndaaaaaaaReceiver'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
game.o: In function `new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `typeinfo name for BattleEndaaaaaaaReceiver'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
game.o: In function `new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `vtable for BattleEndaaaaaaaReceiver'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
gamemapwidget.o: In function `~BattleEndaaaaaaaReceiver':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `BattleEndaaaaaaaReceiver::~BattleEndaaaaaaaReceiver()'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
gamemapwidget.o: In function `new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `BattleEndaaaaaaaReceiver::~BattleEndaaaaaaaReceiver()'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
gamemapwidget.o: In function `new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `BattleEndaaaaaaaReceiver::~BattleEndaaaaaaaReceiver()'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
gamemapwidget.o: In function `std::_Hashtable<BattleEndaaaaaaaReceiver*, BattleEndaaaaaaaReceiver*, std::allocator<BattleEndaaaaaaaReceiver*>, std::__detail::_Identity, std::equal_to<BattleEndaaaaaaaReceiver*>, std::hash<BattleEndaaaaaaaReceiver*>, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<false, true, true> >::_M_erase(std::integral_constant<bool, true>, BattleEndaaaaaaaReceiver* const&)':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `typeinfo for BattleEndaaaaaaaReceiver'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
gamemapwidget.o: In function `new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `typeinfo name for BattleEndaaaaaaaReceiver'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
gamemapwidget.o: In function `new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `vtable for BattleEndaaaaaaaReceiver'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
battle.o: In function `~BattleEndaaaaaaaReceiver':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `BattleEndaaaaaaaReceiver::~BattleEndaaaaaaaReceiver()'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
battle.o: In function `~new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `BattleEndaaaaaaaReceiver::~BattleEndaaaaaaaReceiver()'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
battle.o: In function `~new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `BattleEndaaaaaaaReceiver::~BattleEndaaaaaaaReceiver()'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
battle.o: In function `std::__detail::_Hashtable_alloc<std::allocator<std::__detail::_Hash_node<BattleEndaaaaaaaSender*, false> > >::_M_deallocate_nodes(std::__detail::_Hash_node<BattleEndaaaaaaaSender*, false>*)':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `typeinfo for BattleEndaaaaaaaReceiver'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
battle.o: In function `~new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `typeinfo name for BattleEndaaaaaaaReceiver'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
battle.o: In function `~new_allocator':
/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: multiple definition of `vtable for BattleEndaaaaaaaReceiver'
province.o:/home/michal/Dokumenty/Projekty/build-Universania-Desktop-Debug/../Universania/battle.hpp:10: first defined here
clang: error: linker command failed with exit code 1 (use -v to see invocation)
头文件中的行外函数定义将与包含该头文件的每个编译单元一起发出，因此有多个定义。只要把它改成inline就可以了。
顺便说一句，这与你的宏无关。在c++中应该避免使用宏。除了include保护和条件编译之外，c++中几乎没有什么有意义的宏用法。模板可以更好地完成许多事情。
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