基本實現原理

/* 通過結構體+函數指針模擬類 */
typedef struct {// 成員變量int x;  // 成員方法（函數指針）                  void (*print)(void* self);  
} MyClass;/* 成員函數實現 */
void my_print(void* self) {MyClass* obj = (MyClass*)self;printf("Value: %d\n", obj->x);
}/* 構造函數 */
MyClass* MyClass_create(int x) {MyClass* obj = malloc(sizeof(MyClass));obj->x = x;obj->print = my_print;  // 方法綁定return obj;
}

🔀 三種核心特性實現

1. 封裝

// 頭文件（.h）中只聲明結構體指針
typedef struct HiddenClass HiddenClass;// 源文件（.c）中定義真實結構體
struct HiddenClass {int private_data;void (*public_method)(HiddenClass*);
};

2. 繼承

/* 基類 */
typedef struct {int base_val;void (*base_method)();
} Base;/* 派生類 */
typedef struct {Base super;  // 包含基類實現繼承int derived_val;
} Derived;

3. 多態

typedef struct {void (*speak)();
} Animal;void dog_speak() { printf("汪汪汪\n"); }
void cat_speak() { printf("喵喵喵\n"); }Animal dog = { .speak = dog_speak };
Animal cat = { .speak = cat_speak };

🧩 完整示例：圖形系統

/* 基類：Shape */
typedef struct Shape Shape;
struct Shape {void (*draw)(Shape*);
};/* 派生類：Circle */
typedef struct {Shape parent;  // 繼承int radius;
} Circle;void circle_draw(Shape* self) {Circle* c = (Circle*)self;printf("繪制半徑%d的圓\n", c->radius);
}Circle* create_circle(int r) {Circle* c = malloc(sizeof(Circle));c->parent.draw = circle_draw;c->radius = r;return c;
}

備注

個人水平有限，有問題隨時交流~