C++基础一

main.cpp

#include <Teacher.h>#include <iostream>using namespace std;void fun() {MyTeacher teacher;teacher.setAge(18);teacher.setName("小明");cout << "teacher name : " << teacher.getName() << endl;cout << "teacher age : " << teacher.getAge() << endl;}//值传递void setFunc(MyTeacher teacher) {teacher.setAge(16);teacher.setName("jhone");cout << "teacher name : " << teacher.getName() << endl;cout << "teacher age : " << teacher.getAge() << endl;}//引用传递void setFuncY(MyTeacher &teacher) {teacher.setAge(16);teacher.setName("jhone");cout << "teacher name : " << teacher.getName() << endl;cout << "teacher age : " << teacher.getAge() << endl;}void main() {//fun();//MyTeacher teacher;//teacher.setAge(20);//teacher.setName("小明");MyTeacher teacher = MyTeacher("xiaohong", 25);//没new关键字的是对象MyTeacher *teacher1 = new MyTeacher("xiaohong", 25);//有new关键字是指针 不会走虚构函数 需要自己释放delete teacher1;//释放对象 才会走虚构函数teacher1 = nullptr;cout << "teacher name : " << teacher.getName() << endl;cout << "teacher age : " << teacher.getAge() << endl;setFuncY(teacher);cout << "teacher name : " << teacher.getName() << endl;cout << "teacher age : " << teacher.getAge() << endl;system("pause");}

Teacher.h

#pragma onceclass MyTeacher{public:MyTeacher();//构造函数 (malloc)~MyTeacher();//虚构函数 释放在构造函数里面动态申请的内存 (free)void setAge(int age);int getAge();void setName(char *name);char* getName();private:int age;char *name;};

Teacher.cpp

#include <Teacher.h>#include<iostream>using namespace std;//创建命名空间namespace NSP_A {struct MyStudent{int age;};}MyTeacher::MyTeacher(){std::cout << "MyTeacher 构造函数 " << this << std::endl;}MyTeacher::~MyTeacher(){//使用了std的命名空间 就可以不要前面的std限定符cout << "MyTeacher 虚构函数 " << this << std::endl;}void MyTeacher::setAge(int age) {this->age = age;//命名空间的使用NSP_A::MyStudent t;t.age = 18;using NSP_A::MyStudent;MyStudent t2;t2.age = 16;}int MyTeacher::getAge() {return this->age;}void MyTeacher::setName(char *name) {this->name = name;}char* MyTeacher::getName(){return this->name;}

浅拷贝和深拷贝

MyStudent.h

class MyStudent{public:MyStudent(int age,char*name,char *teacherName);~MyStudent();//重写默认的拷贝构造函数MyStudent(const MyStudent &student);public:int age;char *name;char *teacherName;private:};

MyStudent.cpp

#include <MyStudent.h>#include <iostream>using namespace std;MyStudent::MyStudent(int age, char*name, char *teacherName):age(age),name(name),teacherName(teacherName){cout << "无参构造函数" << this << endl;}MyStudent::~MyStudent(){cout << "虚构函数" << this << endl;}//默认拷贝构造函数 浅拷贝MyStudent::MyStudent(const MyStudent &student) {cout << "拷贝构造函数" << this << endl;this->age = student.age;this->name = student.name;this->teacherName = student.teacherName;}main.cppvoid copyTest() {MyStudent student = MyStudent(21, "jake", "jhone");MyStudent stu2 = student;//也会调用拷贝构造函数}9:58 2017/10/23void main() {copyTest();system("pause");}

注意：浅拷贝可能引出的问题 我在构造函数申请一块内存， 虚构函数去释放这块内存 当我退出时释放内存 由于拷贝的对象是执行的拷贝构造函数 这里没有申请内存 用的是同一块内存 这块内存释放后 执行拷贝对象虚构函数时 会抛出异常 是由野指针造成的 

问题产生

#include <MyStudent.h>#include <iostream>using namespace std;MyStudent::MyStudent(int age, char*name, char *teacherName):age(age){cout << "无参构造函数" << this << endl;int len = strlen(name);this->name = (char *)malloc(len + 1);strcpy(this->name, name);len = strlen(teacherName);this->teacherName = (char *)malloc(len + 1);strcpy(this->teacherName, teacherName);}MyStudent::~MyStudent(){cout << "虚构函数" << this << endl;free(this->name);free(this->teacherName);}//默认拷贝构造函数 浅拷贝MyStudent::MyStudent(const MyStudent &student) {cout << "拷贝构造函数" << this << endl;this->age = student.age;this->name = student.name;this->teacherName = student.teacherName;}

    

解决浅拷贝可能存在的问题 在拷贝函数重新申请空间 就可以了

MyStudent::MyStudent(const MyStudent &student) {cout << "拷贝构造函数" << this << endl;this->age = student.age;//this->name = student.name;int len = strlen(student.name);this->name = (char *)malloc(len + 1);strcpy(this->name, student.name);//this->teacherName = student.teacherName;len = strlen(student.teacherName);this->name = (char *)malloc(len + 1);strcpy(this->name, student.teacherName);}