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在纯虚拟基类中不创建显式函数就无法复制构造?

upcasting downcast deep-copy virtual c++

Nav MetroidFan2002 · 技术社区 · 15 年前

我的目标是做一个类的深度复制,但是一个虚拟类正在引起麻烦。

#include<iostream>
using namespace std;

class Vir//pure virtual class
{
    public:
    virtual void hi()=0;
};

class Handler:public Vir
{
    public:
    int i;
    Handler() {}
    Handler(int val):i(val) {}
    void hi() {cout<<"Value of i="<<i<<endl;}
    int getI() const {return i;}
    void setI(int j) {i=j;}
};

class ControlPanel
{
    public:
    Vir *v;
    ControlPanel(const ControlPanel& c)//copy constructor
    {
        v=new Handler;
        v->setI(c.getI());
    }
    int getI()const {return v->getI();}

    void initialize() {v=new Handler(10);}
    void hi() {v->hi();}
    ControlPanel() {}
    ~ControlPanel() {delete v;}
};

int main()
{
    ControlPanel cc;
    cc.initialize();
    cc.hi();
    ControlPanel bb(cc);//copying cc into bb
}

编译错误消息:

test.cpp: In copy constructor âControlPanel::ControlPanel(const ControlPanel&)â:
test.cpp:28: error: âclass Virâ has no member named âsetIâ
test.cpp: In member function âint ControlPanel::getI() constâ:
test.cpp:30: error: âclass Virâ has no member named âgetIâ

我计划有更多的处理程序类(如handler1、handler2等),这些类继承自VIR,并将拥有自己的唯一成员(如float a或double b等)。所以我把所有处理程序类的getter&setter函数都保存在vir类中是没有意义的。我想将getter和setter方法保留在处理程序类中,因为这些成员对于处理程序类是唯一的。编译器不允许我这样做。帮助?

6 回复 | 直到 15 年前

Community Mohan Dere 9 年前

clone Vir ControlPanel his answer duplicate

class Vir
{
    public:
    virtual Vir* clone() const = 0;
    ...
};

Handler

Handler* Handler::clone() const
{
    return new Handler( *this );
}

Handler::clone Handler* Vir* Vir::clone

ControlPanel( const ControlPanel& c )
    : v( c.v->clone() )
{
}

Andrew Aylett 15 年前

duplicate() copyFrom(Abs other)

luke 15 年前

Factory Pattern Vir RAII

Prasoon Saurav 15 年前

Vir *v Handler *v;

Vir setI() getI()

class Vir//pure virtual class
{
    public:
    virtual void hi()=0;
    virtual int getI()const =0;
    virtual void setI(int)=0;
};

Steve Townsend 15 年前

getI setI Vir

Nav MetroidFan2002 15 年前

#include<iostream>
using namespace std;

class Vir//pure virtual class
{
    public:
    virtual void hi()=0;
    virtual int getI() {std::cout << "Inside Base class" << std::endl;}
    virtual void setI(int i) {cout<<"In base"<<endl;}
    virtual int getX() {}
    virtual void setX(int x) {}
};
class Model
{
    public:
    int x;
    Model(const Model& mm) {x=mm.x;}
    Model():x(555) {cout<<"Model constructor called"<<endl;}
    int getX() {return x;}
    void setX(int xx) {x=xx;}
};

class Handler:public Vir
{
    public:
    int i;
    Model *m;

    Handler() {m=new Model;cout<<"Handler constructor called"<<endl;}
    Handler(const Handler& h)
    {
    std::cout << "Inside Handler @lineNumber:" << __LINE__ << std::endl;
    i=h.i;
    m=new Model(*h.m);
    }
    Handler(int val):i(val) {}
    ~Handler() {delete m;}
    void hi() {cout<<"Value of i="<<i<<endl;}
    int getI() {return i;}
    void setI(int j) {i=j;}
    int getX() {return m->getX();}
    void setX(int xx) {m->setX(xx);}
};

class ControlPanel
{
    public:
    int abc;
    Vir *v;
    ControlPanel(const ControlPanel& c)//copy constructor
    {
    std::cout << "Inside ControlPanel @lineNumber:" << __LINE__ << std::endl;
        v=new Handler((Handler&)*(c.v));
    }
    void initialize() {v=new Handler();v->setI(10);abc=222;}
    void hi() {v->hi();}
    ControlPanel() {}
    ~ControlPanel() {delete v;}
};

int main()
{
    ControlPanel cc;
    cc.initialize();
    cc.hi();    
    cout << "(cc.v)->i::" << (cc.v)->getI() << endl;
    cout<<"x value cc="<<(cc.v)->getX()<<endl;
    ControlPanel bb(cc);//copying cc into bb
    cout << "(bb.v)->i::" << (bb.v)->getI() << endl;
    cout<<"x value bb="<<(bb.v)->getX()<<endl;
    (cc.v)->setI(999);
    (cc.v)->setX(888888888);
    cout << "(cc.v)->i::" << (cc.v)->getI() << endl;
    cout << "(bb.v)->i::" << (bb.v)->getI() << endl;
    cout<<"x value cc="<<(cc.v)->getX()<<endl;
    cout<<"x value bb="<<(bb.v)->getX()<<endl;
}//main
/*
Output:
Model constructor called
Handler constructor called
Value of i=10
(cc.v)->i::10
x value cc=555
Inside ControlPanel @lineNumber:52
Inside Handler @lineNumber:32
(bb.v)->i::10
x value bb=555
(cc.v)->i::999
(bb.v)->i::10
x value cc=888888888
x value bb=555  */