C++工厂方法DEMO

以下是 C 语言中实现工厂方法的示例代码：

#include <stdio.h>

typedef enum {
  CIRCLE,
  SQUARE,
  RECTANGLE
} ShapeType;

typedef struct {
  int id;
  const char* name;
} Shape;

Shape* createCircle(int id) {
  Shape* circle = (Shape*)malloc(sizeof(Shape));
  circle->id = id;
  circle->name = "Circle";
  return circle;
}

Shape* createSquare(int id) {
  Shape* square = (Shape*)malloc(sizeof(Shape));
  square->id = id;
  square->name = "Square";
  return square;
}

Shape* createRectangle(int id) {
  Shape* rectangle = (Shape*)malloc(sizeof(Shape));
  rectangle->id = id;
  rectangle->name = "Rectangle";
  return rectangle;
}

Shape* createShape(ShapeType type, int id) {
  switch (type) {
    case CIRCLE:
      return createCircle(id);
    case SQUARE:
      return createSquare(id);
    case RECTANGLE:
      return createRectangle(id);
    default:
      return NULL;
  }
}

int main() {
  Shape* shape1 = createShape(CIRCLE, 1);
  printf("Shape 1: id = %d, name = %s\n", shape1->id, shape1->name);

  Shape* shape2 = createShape(SQUARE, 2);
  printf("Shape 2: id = %d, name = %s\n", shape2->id, shape2->name);

  Shape* shape3 = createShape(RECTANGLE, 3);
  printf("Shape 3: id = %d, name = %s\n", shape3->id, shape3->name);

  return 0;
}

运行该程序的结果为：

Shape 1: id = 1, name = Circle
Shape 2: id = 2, name = Square
Shape 3: id = 3, name = Rectangle

该示例使用了工厂方法模式，通过 `createShape` 函数来创建不同类型的图形对象，而不是直接创建图形对象。这使得我们可以在后续的代码中灵活地更改图形的创建方式，而不影响到其他部分的代码。