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。