C++对象 继承/封装/多态

Maqi extend Human

class Human {
//默认篇protected类型 不能被外部调用 加上public标志后可直接取
public:
    int weight;
    int height;
public:
//封装性 保护成员安全  与java相同
    int getWeight() {
        return weight;
    }

    virtual int getHeight() {
        return height;
    }
//这个构造函数很先进 可以设置默认参数 类似于Kotiln
public:
    Human(int weight, int height) : weight(weight = 100), height(height = 170) {}

    Human() : weight(weight = 100), height(height = 170) {}
};
//注意 public很重要 如果不公开后面将无法调用Human类的所有成员以及函数，当然他也可以设置成protected类型
class Maqi : public Human {

public:
    string name;
    int age;
    //这里的&没什么作用 因为加不加都表示name变量
    string &getName() {
        return this->name;
    }
    //比较重要 间接调用父类的函数 需要加上 Human::
    int getWeight() {
        return Human::getWeight()+100;
    }
    //构造函数传参 类似于java中的super关键字
    Maqi(int weight, int height) : Human(weight, height) {
        cout << " Maqi()" << endl;
    }
    //同上 这里不予理会Human的构造
    Maqi(string name) : Human() {
        this->name = name;
    }
    //空参构造 和java不同 必须手写
    Maqi() : Human() {
        cout << " Maqi()" << endl;
    }
    //析构函数 delete之后释放
    virtual ~Maqi() {
        cout << name << " ~Maqi()" << endl;
    }
    //这个函数为拷贝函数 默认会生成一个 不建议重写 如果重写可能会出现奇怪的BUG。
    Maqi(Maqi &maqi) : Human() {
        age = maqi.age;
        name = maqi.name;
    }
};

class SuperMan : public Human {
    int getHeight() {
        return height + 100;
    }
};

调用

string *maqi = new string("maqi");
    Maqi *maqis = new Maqi(*maqi);
    cout << "maqis->getWeight() = " << maqis->getWeight() << endl;
    Maqi copyMaqi(*maqis);
    cout << "maqis->getWeight() = " << maqis->Human::getWeight() << endl;
    cout << "==============================================" << endl;
    Maqi changeMqi(copyMaqi);
    cout << "maqis->getWeight() = " << maqis->weight << endl;
    cout << "==============================================" << endl;
    string *change = new string("change");
    cout << "maqis->getWeight() = " << maqis->getWeight() << endl;
    cout << "====================delete==========================" << endl;

    SuperMan superMan;
    superMan.weight = 1000;
    cout << " superMan.height = " << superMan.height << endl;
    cout << " superMan.weight = " << superMan.weight << endl;


    Human *human = &superMan;
    cout << " human.height = " << human->getHeight() << endl;
    cout << " human.weight = " << human->getWeight() << endl;

     delete maqis;
    //delete changeMqi;
    //delete copyMaqi;

总结：
1.maqis->Human::getWeight()为调用父类的函数，比Java麻烦
2.maqis->getWeight()那么就是对父类函数的重写
3. maqis->weight 当Hunam成public之后即可直接调用和java一样。
4.new和delete成对存在，这里之所以注释掉 delete changeMqi; delete copyMaqi;
是因为报“argument given to ‘delete’, expected pointer”
· 5.现在我们新增一个Superman继承Human,使用Human对象接受superman的指针，效果和java是一样的，然而 超人肯定异于常人，需要调用自己的getHeight方法，这时候自用在Human中的getHight前面加上virtual 标志就好了，表明这是一个虚函数，这个和java的抽象函数类似，不过java语言更加严格。