C++第二节（1）:public和private、初始化列表、函数重载

public和private、初始化列表、函数重载

1、初始化列表：

     1.1 在构造函数函数头，对类的成员变量进行初始化

     1.2 ：成员变量（赋给成员变量的值）{}       赋给成员变量的值：形参或常数

2、重载函数：

     2.1函数名一样，参数列表不同（参数类型或参数个数不同）

     2.2 仅仅返回值不同是不可以的

A、public和private

#include <iostream>    //public和privateusing namespace std;class Student{private:    int num;public:    char *name;    Student();    void setValue(int a, char *b);    int getNum();    char * getName();    void print();};Student::Student(){    num = 000;    name = "小强";}void Student::setValue(int a, char *b){    num = a;    name = b;}int Student::getNum(){    return num;}char * Student::getName(){    return name;}void Student::print(){    cout << name << endl;    cout << num << endl;}int main(){    Student a;    //a.name ="小明";  //公有成员变量，可以使用这种形式访问。    //a.num = 123; //私有成员变量,只能通过公有成员函数才可以访问    a.setValue(123456, "小红");    a.print();    cout << a.getNum() << endl;    cout << a.getName() << endl;    return 0;}

B、默认、非默认、初始化列表

Thing.h

#ifndef __C__No727Class__Thing__#define __C__No727Class__Thing__#include <iostream>using namespace std;class Thing{public:    //Thing();  默认构造函数，不带默认值，不能传参    Thing(int a = 10, int b = 20, int c = 30);  //带默认值的默认构造函数，可以传参    //Thing (int m, int n, int p);  //非默认构造函数，自定义的构造函数，传3个参数    ~Thing();    void printThing();private:    int x;    int y;    int z;};#endif /* defined(__C__No727Class__Thing__) */

Thing.cpp

#include "Thing.h"//Thing::Thing()  对无参数的默认构造函数进行实现，初始化//{//    x = 10;//    y = 20;//    z = 30;//}//Thing::Thing(int a, int b, int c)  //对带默认值的默认构造函数进行实现//{//    x = a;//    y = b;//    z = c;//}    //与下面使用初始化列表的语句等价Thing::Thing(int a, int b, int c):x(a), y(b), z(c) {};void Thing::printThing(){    cout << "x = " << x << "y = " << y << "z = " << z << endl;}Thing::~Thing(){    cout << "~~~" << endl;}

main.cpp

#include "Thing.h"int main(int argc, const char * argv[]){    Thing t;    t.printThing();    Thing s(1);    s.printThing();    Thing r(1, 2);    r.printThing();    Thing v(1, 2, 3);    v.printThing();        Thing *y = new Thing(5, 5, 5);  //类类型指针y，指向new的堆空间，堆空间里面是一个对象    (*y).printThing();  //访问方式（*y).和y ->    delete y;    //手工回收内存，把new的堆空间收回，即析构堆空间的对象，此时调用析构函数    return 0;}

C、函数重载

Overload.h

#ifndef __C__No727Class__Overload__#define __C__No727Class__Overload__#include <iostream>using namespace std;class Overload{private:    int x;    int y;    int z;public:    Overload();  //无参数的默认构造函数    Overload(int a, int b, int c);  //自定义函数，下面两个函数是对该函数的重载    Overload(int a, int b);    Overload(int a);    void print();};#endif /* defined(__C__No727Class__Overload__) */

Overload.cpp

#include "Overload.h"Overload::Overload(){    x = 75;    y = 99;    z = 66;}Overload::Overload(int a, int b, int c){    x = a;    y = b;    z = c;}Overload::Overload(int a, int b){    x = a;    y = b;}Overload::Overload(int a){    x = a;}void Overload::print(){    cout << "x = "<< x << "  y = " << y << "  z = " << z <<endl;}

main.cpp

<pre name="code" class="cpp">#include "Overload.h"int main(){    Overload t;      //默认值    t.print();    Overload s(1);   //只传递第一个值，其他值自动置为0    s.print();    Overload r(1, 2);    r.print();    Overload v(1, 2, 3);    v.print();    Overload a;    a = t;           //对象的赋值    a.print();    a = v;    a.print();    return 0;}