Question

我在VS 2008上的c ++下遇到了这种模式的问题。相同的代码已经在gcc中测试过（linux，mac和mingw for widnows）并且它有效。

我在这里复制/粘贴代码：

class MyCommand {

public:
    virtual void execute() = 0;
    virtual ~MyCommand () {};
};

class MyOperation {
public:
    virtual void DoIt() {}; //I also write it not inline
};

class MyOperationDerived : public MyOperation {
public:
    virtual void DoIt() {}; //I also write it not inline
};


class MyUndoStackCommand : public MyCommand {
 public:
     typedef void(MyOperation::*Action)();
     MyUndoStackCommand(MyOperation *rec, Action action);
     /*virtual*/ void execute();
     /*virtual*/ ~MyUndoStackCommand();

private:
    MyOperation *myReceiver;
    Action myAction ;
};

在cpp：

#include "MyUndoStackCommand.h"
#include "MyOperation.h"

MyUndoStackCommand::~MyUndoStackCommand() {
}

MyUndoStackCommand::MyUndoStackCommand(myOperation *rec, Action
action): myReceiver(rec), myAction(action) {
}

void MyUndoStackCommand::execute() {
   ((myReceiver)->*(myAction))();
}

在main.cpp中使用：

MyReceiver receiver;
MyUndoStackCommand usc(&receiver, &MyOperation::DoIt);
usc.execute();

当我在visual studio下调试时，只有直接在MyUndoStackCommand内设置 myAction = &MyOperation::DoIt，它有效，否则无效。

有什么建议吗？

非常感谢你，担

编辑：以下代码使用g ++编译 - Neil Butterworth的更改标记为// NB。

class MyCommand {

public:
    virtual void execute() = 0;
    virtual ~MyCommand () {};
};

class MyOperation {
public:
    virtual void DoIt() {}; //I also write it not inline
};

class MyOperationDerived : public MyOperation {
public:
    virtual void DoIt() {}; //I also write it not inline
};


class MyUndoStackCommand : public MyCommand {
 public:
     typedef void(MyOperation::*Action)();
     MyUndoStackCommand(MyOperation *rec, Action action);
     /*virtual*/ void execute();
     /*virtual*/ ~MyUndoStackCommand();

private:
    MyOperation *myReceiver;
    Action myAction ;
};

MyUndoStackCommand::~MyUndoStackCommand() {
}

MyUndoStackCommand::MyUndoStackCommand(MyOperation *rec,  //NB
                                Action action)
    : myReceiver(rec), myAction(action) {
}

void MyUndoStackCommand::execute() {
   ((myReceiver)->*(myAction))();
}

int main() {
    MyOperation receiver;    //NB
    MyUndoStackCommand usc(&receiver, &MyOperation::DoIt);
    usc.execute();
}

Answer 1

使用Neils编辑，这在Visual Studio 2008中可以正常工作。

// command.h
#pragma once
#include <iostream>      // added for printing
using namespace std;     // added for printing
class MyCommand {
public:
    virtual void execute() = 0;
    virtual ~MyCommand () {};
};
class MyOperation {
public:
    virtual void DoIt() {
        cout << "myoperation::doit()" << endl;
    }; //I also write it not inline
};
class MyOperationDerived : public MyOperation {
public:
    virtual void DoIt() {
        cout << "myoperationderived::doit()" << endl;
    }; //I also write it not inline
};
class MyUndoStackCommand : public MyCommand {
 public:
     typedef void(MyOperation::*Action)();
     MyUndoStackCommand(MyOperation *rec, Action action);
     /*virtual*/ void execute();
     /*virtual*/ ~MyUndoStackCommand();
private:
    MyOperation *myReceiver;
    Action myAction;
};
// command.cpp
#include "command.h"
MyUndoStackCommand::~MyUndoStackCommand() {
}
MyUndoStackCommand::MyUndoStackCommand(/*m*/ MyOperation *rec, Action
action): myReceiver(rec), myAction(action) {
}
void MyUndoStackCommand::execute() {
   ((myReceiver)->*(myAction))();
}
// main.cpp
#include "command.h"
int main(){ 
 MyOperationDerived receiver;
 MyUndoStackCommand usc(&receiver, &MyOperation::DoIt);
 usc.execute();
}

将打印：

"myoperationderived::doit()"

Visual Studio 2008下的命令模式问题（C ++）

1 个答案: