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C++运算符重载与多继承及二义性详解

lpf_wei 人气:0

1.类外运算符重载

class Point {
private:
    int x,y;
public:
    // 系统C++源码,大量使用此方式 :x(x), y(y)
    Point(int x, int y) :x(x), y(y) {}
    // set get 函数
    void setX(int x) {
        this->x = x;
    }
    void setY(int y) {
        this->y = y;
    }
    int getX() {
        return this->x;
    }
    int getY() {
        return this->y;
    }
};
/*类外运算符重载
 * 在真实开发过程中,基本上都是写在类的里面的,外部是不能获取内部的私有成员的
 * */
Point operator + (Point point1,Point point2){
    int x = point1.getX() + point2.getX();
    int y = point1.getY() + point2.getY();

    Point res(x, y);
    return res;
}
int main(){
    Point pointA(10,20);
    Point pointB(10,20);
    Point pointC=pointA+pointB;
    cout << pointC.getX() << " , " << pointC.getY() << endl;
}

日志输出:
20 , 40

两个对象做+法运算就是执行了运算符重载函数

2.类内部运算符号重载

class Point {
private:
    int x,y;
public:
    Point(){}
    // 系统C++源码,大量使用此方式 :x(x), y(y)
    Point(int x, int y) :x(x), y(y) {}
    // set get 函数
    void setX(int x) {
        this->x = x;
    }
    void setY(int y) {
        this->y = y;
    }
    int getX() {
        return this->x;
    }
    int getY() {
        return this->y;
    }
    /*
     * 常量引用:不允许修改,只读模式
     * & 性能的提高,如果没有&  运行+ 构建新的副本,会浪费性能
     * 如果增加了& 引用是给这块内存空间取一个别名而已
     * */
    Point operator + (const Point & point){
        int x=this->x+point.x;
        int y=this->y+point.y;
        return Point(x,y);
    }
    Point operator - (const Point & point){
        int x=this->x-point.x;
        int y=this->y-point.y;
        return Point(x,y);
    }
    void operator ++() { //  ++对象
        this->x = this->x + 1;
        this->y = this->y + 1;
    }
    void operator ++ (int) { // 对象++
        this->x = this->x + 1;
        this->y = this->y + 1;
    }
    /*重载<< 输出运算符号
     * istream 输入 系统的
     * ostream 输出 系统的
     * */
  /*  friend void operator << (ostream & _START,Point &point){
        _START << " 开始输出 " << point.x << " : " << point.y << " 结束了 " << endl;
    }*/
    /*多个<< 连着写 */
  friend ostream & operator << (ostream & _START,Point &point){
      _START << " 开始输出 " << point.x << " : " << point.y << " 结束了 " << endl;
      return _START;
  }
    // istream 输入 系统的
    friend istream & operator >> (istream & _START, Point & point) {
        // 接收用户的输入,把输入的信息
        _START >> point.x >> point.y;
        return _START;
    }
};
int main(){
    Point pointA(30,50);
    Point pointB(10,20);
//    Point pointC=pointA-pointB;
    ++pointA;
//    cout << pointA.getX() << " , " << pointA.getY() << endl;
     cout << pointA << pointB <<endl; // 多个的
    Point pointC;
    cin >> pointC; // >> 是我们自己重载的哦
    cout << "你输入的是:" << pointC.getX() << endl;
    cout << "你输入的是:" << pointC.getY() << endl;
}

3.[] 运算符号重载

class ArrayClass {
private:
    int size =0 ; // 大小  开发过程中,给size赋默认值,不然可能会出现,无穷大的问题
    int * arrayValue; // 数组存放 int 类型的很多值
public:
    ArrayClass(){
        /*指针类型必须分配空间*/
        arrayValue= static_cast<int *>(malloc(sizeof(int *) * 10));
    }
    void set(int index, int value) {
        arrayValue[index] = value; // []目前不是我的
        size+=1;
    }
    int getSize() { // size成员的目标:是为了循环可以遍历
        return this->size;
    }
    // 运算符重载 [index]
    int operator[](int index) {
        return this->arrayValue[index]; // 系统的
    }
};
// 输出容器的内容
void printfArryClass(ArrayClass arrayClass) {
    cout << arrayClass.getSize() << endl;
    for (int i = 0; i < arrayClass.getSize(); ++i) {
        cout << arrayClass[i] << endl; // []是我们自己的 重载符号
    }
}
int main(){
    ArrayClass arrayClass;  // 栈区    实例出来的对象,是在堆区了
    arrayClass.set(0, 100);
    arrayClass.set(1, 200);
    arrayClass.set(2, 300);
    arrayClass.set(3, 400);
    arrayClass.set(4, 500);
    printfArryClass(arrayClass);
}

4.c++继承

class Person {
public:
    char *name;
    int age;
public:
    Person(char *name, int age) : name(name) {
        this->age = age;
        cout << "Person 构造函数" << endl;
    }
    void print() {
        cout << this->name << " , " << this->age << endl;
    }
};
class Student : public Person {
private:
    char * course;
public:
    Student(char * name, int age, char* course) : Person(name, age) , course(course) {
        cout << "Student 构造函数" << endl;
    }
    void test() {
        cout << name << endl;
        cout << age << endl;
        print();
    }
};

5.多继承

class BaseActivity1 {
public:
    void onCreate() {
        cout << "BaseActivity1 onCreate" << endl;
    }
    void onStart() {
        cout << "BaseActivity1 onStart" << endl;
    }
    void show() {
        cout << "BaseActivity1 show" << endl;
    }
};
class BaseActivity2 {
public:
    void onCreate() {
        cout << "BaseActivity2 onCreate" << endl;
    }
    void onStart() {
        cout << "BaseActivity2 onStart" << endl;
    }
    void show() {
        cout << "BaseActivity2 show" << endl;
    }
};
// 子类 继承 二个父类
class MainActivity1 : public BaseActivity1, public BaseActivity2{
public:
    void onCreate() {
        cout << "MainActivity1 onCreate" << endl;
    }
    void onStart() {
        cout << "MainActivity1 onStart" << endl;
    }
    void showSonInfo() {
        cout << "MainActivity1 showSonInfo" << endl;
    }
   // void show() {
     //   cout << "MainActivity1 show" << endl;
    //}
};
int main(){
    // 这个是优先寻找子类的函数,因为特别明确,没有问题,还没有产生歧义(二义性)
    MainActivity1 mainActivity1; // 子类
    mainActivity1.onCreate();
    mainActivity1.onStart();
    mainActivity1.showSonInfo();
    // 不明确,二义性,歧义  /*request for member ‘show' is ambiguous*/
//     mainActivity1.show();
    /*解决二义性 通过.来引出父类 然后再调用*/
    mainActivity1.BaseActivity3::show();
    mainActivity1.BaseActivity2::show();
    mainActivity1.BaseActivity1::show();
    // 解决方案二: 子类上 重写父类的show函数
    mainActivity1.show();
}

6.通过虚继承来解决二义性问题

// 祖父类
class Object{
public:
    int number;
    void show() {
        cout << "Object show run..." << endl;
    }
};
// 父类1
class BaseActivity1 : virtual public Object {
};
// 父类2
class BaseActivity2 : virtual public Object {
};
// 子类
class Son : public BaseActivity1, public BaseActivity2 {
};
int main(){
    Object object;
    BaseActivity1 baseActivity1;
    BaseActivity2 baseActivity2;
    Son son;
    object.number = 100;
    baseActivity1.number = 200;
    baseActivity2.number = 300;
    son.number = 400;
    object.show();
    baseActivity1.show();
    baseActivity2.show();
    son.show();
    cout << object.number << endl;
    cout << baseActivity1.number << endl;
    cout << baseActivity2.number << endl;
    cout << son.number << endl;
}

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