类对象定义 三

Posted 2020-11-23 wuyanzu

浅拷贝

浅拷贝：拷贝后，两个对象会共同指向一个地址，如果有一个对象更改了数据，另一个对象也会受影响，删除对象话，可能会导致释放两次

#include <iostream>

using namespace std;
//.h
class student {
public:
    student();
    student(string name);
    student(const student &stu);
    ~student();
    string getName();
    int age;
private:
    string m_name;
};

//cpp  这叫定义
student::student() {
    m_name="kitty";
    m_p=new int[5];
    cout<<"gou zao"<<endl;
}
string student::getName(){
    return m_name;
}
student::student(string name) {
    m_name=name;
}
//拷贝构造函数 （浅拷贝）
student::student(const student &stu) {
// 如果通过  student stu1=stu  这样的方式创建度对象，会执行拷贝构造函数
    m_name=stu.m_name; //浅拷贝
    m_p=stu.m_p;//浅拷贝 将复制的对象的 指针拷贝给了 另一个对象， 现在两个对象 共同指向了一个 地址

    cout<<"qian kaobei"<<endl;
}
student::~student() {
    delete []m_p; //这样删除的话，浅拷贝会出问题
    cout<<"xi gou"<<endl;
}
void student::printAddr() {
    cout<<"dizhi:"<<*m_p<<endl;
}
void test(student s){

}
int main() {
    student s;
    student s1(s);
    
    s.printAddr();
    s1.printAddr();

    return 0;
}

深拷贝

#include <iostream>
#include <cstdlib>

using namespace std;
//.h
class student {
public:
    student();
    student(string name);
    student(const student &stu);
    ~student();
    string getName();
    void printAddr();
private:
    int count;
    string m_name;
    int *m_p;
};

//cpp  这叫定义
student::student() {
    m_name="kitty";
    count=5;
    m_p=new int[count]; //初始化数组
    for (int i = 0; i < 5; i++) {//数组赋值
        m_p[i]=i;
        cout<<"value:"<<m_p[i]<<endl;
    }
    cout<<"gou zao"<<endl;
}
string student::getName(){
    return m_name;
}
student::student(string name) {
    m_name=name;
}
//拷贝构造函数 （深拷贝）
student::student(const student &stu) {
    count=stu.count;
    //深拷贝 重新开辟一块内存空间
    m_p=new int [count];
    for (int i = 0; i <count; i++)
    {
        m_p[i]=stu.m_p[i];
    }
    cout<<"shen kaobei"<<endl;
}
student::~student() {
    delete []m_p;
    cout<<"xi gou"<<endl;
}
void student::printAddr() {
    cout<<"dizhi:"<<m_p<<endl;
}

void test(student s){

}
int main() {
    student s;
    student s1(s);
    s.printAddr();
    s1.printAddr();
    return 0;
}

对象指针

int main() {
    student *s=new student();
    s->printAddr();
    student *s1=new student();
    (*s1).printAddr();
    return 0;
}

对象成员指针

对象成员指针 类似JAVA中的 对象属性
例如：private Bean bean;
指针类型大小为：4

#include <iostream>
#include <cstdlib>

using namespace std;


class Teacher {
public:
    Teacher(string name, int age);

    ~Teacher();

    string getName();

    int getAge();

private:
    string m_Name;
    int m_Age;
};


//.h
class Student {
public:
    Student(string nameA, int ageA, string nameB , int ageB);

    ~Student();

    void printInfo();

private:
    Teacher *m_teacherA;
    Teacher *m_teacherB;
};


Teacher::Teacher(string name, int age) {
    m_Name = name;
    m_Age = age;
    cout << "Teacher gou zao name: " << m_Name << " age: " << m_Age << endl;
}

Teacher::~Teacher() {
    cout << "Teacher xi gou name: " << m_Name << " age: " << m_Age << endl;
}

int Teacher::getAge() {
    return m_Age;
}

string Teacher::getName() {
    return m_Name;
}


//cpp  这叫定义
Student::Student(string nameA, int ageA, string nameB , int ageB)  {

    m_teacherA=new Teacher(nameA,ageA);
    m_teacherB=new Teacher(nameB,ageB);
    cout << "Student gou zao" << endl;
}

Student::~Student() {
    delete m_teacherA;
    delete m_teacherB;
    cout << "Student xi gou" << endl;
}
void Student::printInfo() {
    cout << "printInfo" << endl;

    cout << "( A: " <<m_teacherA->getName()<<","<<m_teacherA->getAge()<<")"<< endl;

    cout << "( B: " <<m_teacherB->getName()<<","<<m_teacherB->getAge()<<")"<< endl;
}

int main() {

    Student *s=new Student("kitty",20,"tony",22);
    (*s).printInfo();
    cout<< sizeof(s)<<endl;
    cout<< sizeof(Student)<<endl;
    delete s;
    return 0;
}

输出结果：
Teacher gou zao name: kitty age: 20
Teacher gou zao name: tony age: 22
Student gou zao
printInfo
( A: kitty,20)
( B: tony,22)
4
8
Teacher xi gou name: kitty age: 20
Teacher xi gou name: tony age: 22
Student xi gou

this 指针

和JAVA中的this指针差不多一个意思