C++ 指向函数作为参数的指针。数据类型不兼容

Question

我在查找代码中的错误原因时遇到了一些麻烦，我想向您寻求帮助。我昨天已经问过类似的问题，但后来我想我找到了原因。今天早上编译器再次证明我错了......

错误说：

IntelliSense: argument of type "void (Transaction::*)()" is incompatible with parameter of type "eventPointer"

error C2664: 'Calendar::calendarPush' : cannot convert parameter 3 from 'void (__thiscall Transaction::* )(void)' to 'eventPointer'

导致错误的代码可以在 eb 中找到

Main.cpp, line (calling of the method)
Calendar::calendarPush(1, 1, &Transaction::event1);

和

Calendar.cpp line (definition of the method)
void Calendar::calendarPush(double Time, int Priority, eventPointer event)

eventPointer的定义见

Calendar.h, line
typedef void (Calendar::*eventPointer) ();

我看不出这两者是如何不相容的。怎么了？ ：/

代码如下：

----------MAIN.CPP----------

#include <iostream>

#include "Calendar.cpp"
#include "Transaction.cpp"

using namespace std;

int main() {

    cout << "Initializing" << endl;

    double Time = 0.0;
    int Priority = 0;

    cout << "Pushing initial event" << endl;

    Calendar::calendarPush(1, 1, &Transaction::event1);

}

----------CALENDAR.H----------

#include <iostream>
#include <queue>

using namespace std;

class Calendar;

typedef void (Calendar::*eventPointer) ();

struct activationRecord {
    double Time;
    int Priority;
    eventPointer activationEvent;
};


bool operator < (const activationRecord & a, const activationRecord & b);

class Calendar {

private:
    static std::priority_queue<activationRecord> activationCalendar;

public:
    bool calendarEmpty();

    static void calendarPush(double, int, eventPointer);

    activationRecord calendarTop();
    void calendarPop();

    void calendarRun();
};


----------CALENDAR.CPP-----------

#include "Calendar.h"

bool Calendar::calendarEmpty() {

    return activationCalendar.empty();
}

void Calendar::calendarPush(double Time, int Priority, eventPointer event) {

    activationRecord record;

    record.Time = Time;
    record.Priority = Priority;
    record.activationEvent = event;

    activationCalendar.push(record);
}

activationRecord Calendar::calendarTop() {

    return activationCalendar.top();
}

void Calendar::calendarPop() {

    activationCalendar.pop();
}

void Calendar::calendarRun() {

    activationRecord record;

    while(!calendarEmpty()) {
        record = calendarTop();
        calendarPop();

        cout << record.Time << endl;
        cout << record.Priority << endl;
        cout << record.activationEvent << endl << endl; 

    }
}

bool operator < (const activationRecord & a, const activationRecord & b) {
    return a.Time > b.Time;
}

----------TRANSACTION.H----------

#include <iostream>

using namespace std;


class Transaction {

public:
    void event1();
    void event2();
    void event3();
    void event4();
    void event5();

};

----------TRANSACTION.CPP-----------

#include <iostream>

#include "Transaction.h"

using namespace std;

void event1() {

    cout << "event1" << endl;


}

void event2() {

    cout << "event2" << endl;


}

void event3() {

    cout << "event3" << endl;


}

void event4() {

    cout << "event4" << endl;


}

void event5() {

    cout << "event5" << endl;
}

---

现在突然间我遇到了更多的错误，这对我来说更没有意义。

error C2027: use of undefined type 'Transaction'

error C2065: 'event1' : undeclared identifier

error C2011: 'Transaction' : 'class' type redefinition

我只是不明白怎么会发生这样的事情，这似乎与我的代码包含的内容直接不一致。

我宁愿再次粘贴整个代码，以防我搞砸了我看不到的东西：

----------MAIN.CPP----------

#include <iostream>

#include "Calendar.h"
#include "Transaction.h"

using namespace std;

int main() {

    cout << "Inicializuji" << endl;

    double Time = 0.0;
    int Priority = 0;

    cout << "Vlkadam uvodni udalost" << endl;

    Calendar::calendarPush(1, 1, &Transaction::event1);

}

----------CALENDAR.H----------

#include <iostream>
#include <queue>

#include "Transaction.h"

using namespace std;

typedef void (Transaction::*eventPointer) ();

struct activationRecord {
    double Time;
    int Priority;
    eventPointer activationEvent;
};


bool operator < (const activationRecord & a, const activationRecord & b);

class Calendar {

private:
    static std::priority_queue<activationRecord> activationCalendar;

public:
    bool calendarEmpty();

    static void calendarPush(double, int, eventPointer);

    activationRecord calendarTop();
    void calendarPop();

    void calendarRun();
};


----------CALENDAR.CPP-----------

#include "Calendar.h"

bool Calendar::calendarEmpty() {

    return activationCalendar.empty();
}

void Calendar::calendarPush(double Time, int Priority, eventPointer event) {

    activationRecord record;

    record.Time = Time;
    record.Priority = Priority;
    record.activationEvent = event;

    activationCalendar.push(record);
}

activationRecord Calendar::calendarTop() {

    return activationCalendar.top();
}

void Calendar::calendarPop() {

    activationCalendar.pop();
}

void Calendar::calendarRun() {

    activationRecord record;

    while(!calendarEmpty()) {
        record = calendarTop();
        calendarPop();

        cout << record.Time << endl;
        cout << record.Priority << endl;
        cout << record.activationEvent << endl << endl; 

    }
}

bool operator < (const activationRecord & a, const activationRecord & b) {
    return a.Time > b.Time;
}   

----------TRANSACTION.H----------

#include <iostream>

using namespace std;

class Transaction {

public:
    void event1();
};


----------TRANSACTION.CPP-----------

#include "Transaction.h"

using namespace std;

void Transaction::event1() {

}   

请帮忙。

Answer 1

问题是因为它们是指向成员函数的指针。尽管它们具有相同的返回类型和参数类型，但它们被认为是不同的类型，因为它们是不相关类的成员。

当您指定您的参数为void (Calendar::*)() 类型时，只有Calendar 的成员函数可以转换为它。

解决问题的一种方法是让Calendar 使用void (*)() 而不是void (Calendar::*)()。然后将Transaction的event成员函数改为static函数。然后event 函数的类型将是void (*)() 而不是void (Transaction::*)()。

另一种方法是将eventPointer 更改为void (Transaction::*)() 类型，以便转换工作。此外，您的Transaction.cpp 目前似乎定义了void event1(); 而不是void Transaction::event1();，这将导致一些未定义的函数相关错误。