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 once
class 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.cpp

void copyTest() {
	MyStudent student = MyStudent(21, "jake", "jhone");
	MyStudent stu2 = student;//也会调用拷贝构造函数
}9:58 2017/10/23

void 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);
}

猜你喜欢