代理模式

一、代理模式

二、虚代理

#include <iostream>
#include <unistd.h>

using namespace std;

class Text
{
public:
    void showText()
    {
        cout << "good sentence" << endl;
    }
};

class ImageSubject
{
public:
    virtual void showImage() = 0;
};

class BigImage : public ImageSubject
{
public:
    BigImage()
    {
        sleep(6);
        cout << "load done, show" << endl;
    }

    void showImage()
    {
        cout << "Image is shown" << endl;
    }
};

class ProxyImage : public ImageSubject
{
public:
    ProxyImage()
    {
        bi = NULL;
    }

    void showImage()
    {
        if (bi == NULL) bi = new BigImage;
        bi->showImage();
    }

private:
    BigImage * bi;
};

class Doc
{
public:
    Doc()
    {
        t = new Text;
        pi = new ProxyImage;
    }

    void show()
    {
        t->showText();
        pi->showImage();
    }

private:
    Text * t;
    ProxyImage * pi;
};

int main()
{
    Doc d;
    d.show();

    return 0;
}

三、智能代理

• 智能指针的使用，自动析构——

#include <iostream>
#include <memory>

using namespace std;

class A
{
public:
    A()
    {
        cout << "A()" << endl;
    }

    ~A()
    {
        cout << "~A()" << endl;
    }

    void dis()
    {
        cout << "auto_ptr" << endl;
    }
};

class SmartPointer
{
public:
    SmartPointer(A *pa) : _pa(pa) {}
    ~SmartPointer()
    {
        delete _pa;
    }

    A* &operator->()
    {
        return _pa;
    }

    A &operator*()
    {
        return *_pa;
    }

private:
    A * _pa;
};

// ap是对象A的代理
void func()
{
//    auto_ptr<A> ap(new A);
//    ap->dis();

    SmartPointer sp(new A);
    sp->dis();
    (*sp).dis();
}


int main()
{
//    A a;
//    a.dis();

    func();

    return 0;
}