C言語で異なる構造体のポインタの配列

Question

同じサイズの異なる構造体のポインタの配列を持つことは可能ですか？はいの場合は、配列から構造体の変数やメンバーにアクセスできますか？いくつか例を挙げることができますか？

おかげ

Answer 1

厳密にあなたがすることはできません話します。しかし、base構造へのポインタを保持することができます！

// http://ideone.com/FhSULX 

#include <stdio.h> 


struct BaseFigure 
{ 
    int type; 
    const char * name; 
}; 

struct RectangleFigure 
{ 
    struct BaseFigure base; // must be first field! 
    int width, height; 
}; 

struct CircleFigure 
{ 
    struct BaseFigure base; // must be first field! 
    float radius; 
}; 

enum {FIGURE_RECTANGLE, FIGURE_CIRCLE}; 

int main() 
{ 
    enum {FIGURE_COUNT = 2}; 

    struct BaseFigure *arrayOfFigures[FIGURE_COUNT]; 
    struct RectangleFigure rectangle; 
    struct CircleFigure circle; 
    int i; 

    rectangle.base.name = "rectangle"; 
    rectangle.base.type = FIGURE_RECTANGLE; 
    rectangle.width = 10; 
    rectangle.height = 20; 

    circle.base.name = "circle"; 
    circle.base.type = FIGURE_CIRCLE; 
    circle.radius = 3.5f; 

    arrayOfFigures[0] = (struct BaseFigure*)&rectangle; 
    arrayOfFigures[1] = (struct BaseFigure*)&circle; 

    for (i = 0; i < FIGURE_COUNT; i++) 
    { 
     struct BaseFigure * const baseFigure = arrayOfFigures[i]; 
     printf("Figure type: %d, name: %s\n", baseFigure->type, baseFigure->name); 
     switch (baseFigure->type) 
     { 
      case FIGURE_RECTANGLE: 
      { 
       struct RectangleFigure * const figure = (struct RectangleFigure*)baseFigure; 
       printf("%s: width: %d, height: %d\n", figure->base.name, 
        figure->width, figure->height); 
      } 
      break; 

      case FIGURE_CIRCLE: 
      { 
       struct CircleFigure * const figure = (struct CircleFigure*)baseFigure; 
       printf("%s: radius: %f\n", figure->base.name, 
        figure->radius); 
      } 
      break; 

      default: 
       printf("Error: unknown figure with type '%d'!\n", baseFigure->type); 
     } 
    } 

    return 0; 
}