Hack cpp Class and Structs

Class 和 Structs

Structs

结构和类的区别：

结构体的参数默认访问为public； 类的参数默认访问是private

结构体继承默认是public继承；类的继承默认是private

都可以有成员变量和成员函数

struct Student{
    string age;
    string first_name;
    string last_name;
    string standard;
};
int main(){
    Student st;
}

struct里也可以重载运算符

struct Workshops{
    int start_time;
    int duration;
    int end_time;
    bool operator<(const Workshops &rhs){
        return (this->end_time < rhs.end_time);
    }
};

class

c++ 是面向对象设计的程序语言

1. public: Public members (variables, methods) can be accessed from anywhere the code is visible.
2. private: Private members can be accessed only by other member functions, and it can not be accessed outside of class.

class SampleClass {
    private:
        int val;
    public:
        void set(int a) {
            val = a;
        }
        int get() {
            return val;
        }
};

类里的参数初始化

使用类名+(){

}

多态

多态：同一个行为具有多个不同表现形式或形态的能力，表现为： 重载和覆盖

1. 重载： 重载指再相同作用域中存在多个同名函数，这些函数的参数表不同，编译器可以根据不同的参数表选择不同的同名函数。

2. 覆盖：函数名，返回值，参数表都相同，子类重写从基类继承过来的函数

举例：

class Box{
public:
    int l,b,h;
    Box(){ //重载
        l=0;
        b=0;
        h=0;
    }
    Box(int aa, int ab, int ac){//重载
        l = aa;
        b = ab;
        h = ac;
    }
    Box(const Box& temp){//重载
        l=temp.l;
        b=temp.b;
        h = temp.h;
    }
    int getLength(){
        return l;
    }    
    int getBreadth(){
        return b;
    }
    int getHeigth(){
        return h;
    }
    long long CalculateVolume(){
        return (long long)l*b*h;
    }
    bool operator<(Box& temp){// 对操作符的重载
        if(this->l<temp.l){
            return true;
        }
        else if (this->b<temp.b&&this->l==temp.l) {
            return true;
        }else if (this->b<temp.b&&this->l==temp.l&&this->h<temp.h) {
            return true;
        }else {
            return false;
        }
        
        
    }
    friend ostream& operator<<(ostream& out, Box& B){// 对操作符的重载，"<<"需要用到ostream& 
        out<<B.l<<" "<<B.b<<" "<<B.h;
        return out;
    }
    
};