c++面向对象之封装

c++面向对象三大特性：封装、继承、多态；

封装的意义：

将属性和行为作为一个整体，表现生活中的事物；
将属性和行为加以权限控制；

#include<iostream>
using namespace std;

class Student {
public:
    string name;
    int age;
    double score;
    void show() {
        cout << "姓名：" << name << endl;
        cout << "年龄：" << age << endl;
        cout << "分数：" << score << endl;
    }
    void setName(string name) {
        this->name = name;
    }
    void setAge(int age) {
        this->age = age;
    }
    void setScore(double score) {
        this->score = score;
    }
    string getName() {
        return this->name;
    }
    int getAge() {
        return this->age;
    }
    double getScore() {
        return this -> score;
    }
};

int main() {
    Student s1;
    s1.name = "tom";
    s1.age = 12;
    s1.score = 99.0;
    s1.show();
    s1.setName("jack");
    s1.setAge(22);
    s1.setScore(100.0);
    cout << s1.getName() << endl;
    cout << s1.getAge() << endl;
    cout << s1.getScore() << endl;
    s1.show();
    system("pause");
    return 0;
}

输出：

c++中的访问权限：

public：类内可以访问，类外可以访问；
private：类内可以访问，类外不可以访问；子类可以访问父类的保护内容；
protected：类内可以访问，类外不可以访问；子类不可以访问父类的保护内容；

#include<iostream>
using namespace std;

class Student {
private:
    string name;
    int age;
    double score;
public:
    void setName(string name) {
        this->name = name;
    }
    void setAge(int age) {
        this->age = age;
    }
    void setScore(double score) {
        this->score = score;
    }
    string getName() {
        return this->name;
    }
    int getAge() {
        return this->age;
    }
    double getScore() {
        return this -> score;
    }
    void show() {
        cout << "姓名：" << name << endl;
        cout << "年龄：" << age << endl;
        cout << "分数：" << score << endl;
    }
};

int main() {
    Student s1;
    /* 此时这样访问会报错
    s1.name = "tom";
    s1.age = 12;
    s1.score = 99.0;
    */
    s1.show();
    //可以通过set和get方法去操作成员私有变量
    s1.setName("jack");
    s1.setAge(22);
    s1.setScore(100.0);
    cout << s1.getName() << endl;
    cout << s1.getAge() << endl;
    cout << s1.getScore() << endl;
    s1.show();
    system("pause");
    return 0;
}

输出：

对于全局变量，如若不初始化，都会默认有一个固定的值；对于局部变量，如若不初始化，默认会有一个随机值。