出于某種原因，我無法使用附加到“Broker”物件的“getNotify()”函式。我在不作業的行中添加了一條評論（在“發布者”類中）。作為錯誤，我收到“錯誤；不允許指向不完整型別別的指標”請幫助
“Broker”類是用 Singleton-Pattern Broker.h 類實作的：
#ifndef DEF_Broker
#define DEF_Broker
#include <iostream>
#include "classes.h"
using namespace std;
class Broker : Publisher
{
static Broker *instance;
Broker();
public:
static Broker* getInstance()
{
if(!instance)
{
instance = new Broker();
}
return instance;
}
void getNotify()
{
for(auto sub : SubscriberList)
{
if(t.msg == "Hello World")
{
SubCount ;
cout << SubCount << " - ";
sub->update(t.msg);
}
else if(t.msg == "Ping")
{
cout << "Ping" << endl;
sub->update("Pong");
}
}
}
};
Broker *Broker::instance = 0; // Null, because instance will be initialized on demand.
Broker::Broker(){}; // Private constructor so that no objects can be created.
#endif
類.h：
#ifndef DEF_classes
#define DEF_classes
#include <iostream>
#include <list>
using namespace std;
class Broker;
class Subscriber
{
public:
void update(string msg)
{
cout << msg << endl;
}
};
class Topic
{
public:
string msg;
Topic(){};
Topic(string msg)
{
this->msg = msg;
}
};
class Publisher
{
protected:
list<Subscriber*> SubscriberList;
static int SubCount;
public:
Topic t;
Broker *broker;// = broker->getInstance();
Publisher(){}
Publisher(Topic t)
{
this->t = t;
};
void AddSub(Subscriber *sub)
{
SubscriberList.push_back(sub);
}
void notify(string msg)
{
broker->getNotify(); // this not working
}
};
int Publisher::SubCount = 0; // Initialize static member SubCount
#endif
uj5u.com熱心網友回復：
通常您需要在 classes.h 中包含 broker.h，但是，這會創建回圈依賴。
因此，在 .cpp 檔案中實作 Publisher 的功能，并在該檔案中包含 broker.h。classes.h (class broker;) 中的前向宣告需要保留。
uj5u.com熱心網友回復：
解決此問題的一種可能方法是為不同的類創建不同的檔案（頭檔案和源檔案）。在這種情況下，我已經為您完成了這項作業，以便您可以將此示例作為您未來目的/程式的參考（起點）。以下是所有檔案：
檔案名
#ifndef DEF_Broker
#define DEF_Broker
#include <iostream>
#include "Publisher.h"
class Broker : Publisher
{
static Broker *instance;
Broker();
public:
static Broker* getInstance()
{
if(!instance)
{
instance = new Broker();
}
return instance;
}
void getNotify();
};
#endif
經紀人.cpp
#include "Broker.h"
#include "Subscriber.h"
Broker *Broker::instance = 0; // Null, because instance will be initialized on demand.
void Broker::getNotify()
{
for(auto sub : SubscriberList)
{
if(t.msg == "Hello World")
{
SubCount ;
std::cout << SubCount << " - ";
sub->update(t.msg);
}
else if(t.msg == "Ping")
{
std::cout << "Ping" << std::endl;
sub->update("Pong");
}
}
}
Broker::Broker()
{
}; // Private constructor so that no objects can be created.
主題.h
#ifndef TOPIC_H
#define TOPIC_H
#include <iostream>
#include <list>
#include <string>
class Topic
{
public:
std::string msg;
Topic(){}
Topic(std::string msg);
};
#endif
主題.cpp
#include "Topic.h"
Topic::Topic(std::string msg)
{
this->msg = msg;
}
發布者.h
#ifndef PUBLISHER_H
#define PUBLISHER_H
#include <list>
#include "Topic.h"
class Broker;//needed for Borker *broker
class Subscriber;//needed for Subscriber*
class Publisher
{
protected:
std::list<Subscriber*> SubscriberList;
static int SubCount;
public:
Topic t;
Broker *broker;// = broker->getInstance();
Publisher(){}
Publisher(Topic t)
{
this->t = t;
};
void AddSub(Subscriber *sub);
void notify(std::string msg);
};
#endif
發布者.cpp
#include "Publisher.h"
#include "Broker.h"//needed for broker->getNotify()
int Publisher::SubCount = 0; // Initialize static member SubCount
void Publisher::notify(std::string msg)
{
broker->getNotify(); // this not working
}
void Publisher::AddSub(Subscriber *sub)
{
SubscriberList.push_back(sub);
}
訂閱者.h
#ifndef SUBSCRIBER_H
#define SUBSCRIBER_H
#include <string>
class Subscriber
{
public:
void update(std::string msg);
};
#endif
訂閱者.cpp
#include "Subscriber.h"
#include <iostream>
void Subscriber::update(std::string msg)
{
std::cout << msg << std::endl;
}
程式編譯成功，可以在這里看到。
uj5u.com熱心網友回復：
@Ben @AnnopRana 謝謝你們。我從你的回答中得到了啟發，我得到了以下解決方案
經紀人.h
#ifndef DEF_Broker
#define DEF_Broker
#include <iostream>
#include "classes.h"
using namespace std;
class Broker
{
static Broker *instance;
Broker();
public:
Publisher pub;
static Broker* getInstance()
{
if(!instance)
{
instance = new Broker();
}
return instance;
}
void getNotify()
{
for(auto sub : pub.SubscriberList)
{
if(pub.t.msg == "Hello World")
{
pub.SubCount ;
cout << pub.SubCount << " - ";
sub->Subscriber::update(pub.t.msg);
}
else if(pub.t.msg == "Ping")
{
cout << "Ping" << endl;
sub->Subscriber::update("Pong");
}
else
{
cout << "no such as topic" << endl;
}
}
}
};
Broker *Broker::instance = 0; // Null, because instance will be initialized on demand.
Broker::Broker(){}; // Private constructor so that no objects can be created.
#endif
類.h
#ifndef DEF_classes
#define DEF_classes
#include <iostream>
#include <list>
using namespace std;
class Broker;
class Subscriber
{
public:
void update(string msg)
{
cout << msg << endl;
}
};
class Topic
{
public:
string msg;
Topic(){};
Topic(string msg)
{
this->msg = msg;
}
};
class Publisher
{
public:
list<Subscriber*> SubscriberList;
static int SubCount;
Topic t;
Publisher(){}
Publisher(Topic t)
{
this->t = t;
};
void AddSub(Subscriber *sub);
void notify(Broker *b);
};
#endif
發布者.cpp
#include "classes.h"
#include "Broker.h"//needed for broker->getNotify()
using namespace std;
int Publisher::SubCount = 0; // Initialize static member SubCount
void Publisher::notify(Broker *b)
{
b->getNotify();
}
void Publisher::AddSub(Subscriber *sub)
{
SubscriberList.push_back(sub);
}
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