> For the complete documentation index, see [llms.txt](https://docs.1l.lol/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.1l.lol/oop/classes.md).

# 面向对象与类

### 面向对象思想

面向对象（OOP）把数据和操作数据的方法封装在一起，形成**对象**。三大特性：

* **封装**：隐藏内部细节，只暴露必要接口
* **继承**：子类复用父类的属性和方法
* **多态**：同一接口有不同实现

### 类的定义与创建

```cpp
#include <iostream>
using namespace std;

class Student {
private:                  // 私有成员，外部不可直接访问
    string name;
    int score;

public:
    Student(string n, int s) : name(n), score(s) {}  // 构造函数

    void print() {        // 成员函数
        cout << name << " " << score << endl;
    }

    int getScore() { return score; }
};

int main() {
    Student a("Tom", 95); // 创建对象
    a.print();
    return 0;
}
```

### 访问权限

| 关键字         | 说明          |
| ----------- | ----------- |
| `private`   | 仅类内部可访问（默认） |
| `public`    | 任何地方可访问     |
| `protected` | 类内部及子类可访问   |

### 继承

```cpp
class Person {
public:
    string name;
    void hello() { cout << "I am " << name << endl; }
};

class Student : public Person {   // 继承
public:
    int grade;
};
```

### 多态（虚函数）

```cpp
class Animal {
public:
    virtual void speak() { cout << "..." << endl; }
};
class Dog : public Animal {
public:
    void speak() override { cout << "Woof" << endl; }
};
```

### 要点

* 构造函数与类同名、无返回值，用于初始化对象。
* 封装让数据更安全，继承让代码可复用，多态让程序更灵活。


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