链表内容的C调用功能 [英] C calling function on contents of linked list

问题描述

我正在使用GLib管理链接列表.我声明了2个结构，并将它们放置在链接列表中，如下所示.

I am using GLib to manage a linked list. I am declaring 2 structs and the placing them in a linked list as follows.

Asteroid asteroid = {0,0,50,50,50}
Asteroid asteroids = {0,0,200,200,50};

GList *asteroidList = NULL;
asteroidList = g_list_append(asteroidList, &asteroid);
asteroidList = g_list_append(asteroidList, &asteroids);

然后，我使用以下函数遍历列表和calla函数，该函数将结构作为一个圆形绘制到屏幕上，如下所示:

Then i use the following function to traverse the list and calla function that draws the struct to the screen as a circle as follows

void drawAsteroids(){
GList *list = asteroidList;
while(list != NULL){
    printf("Asteroids");
    GList *next = list->next;
    drawAsteroid(list->data);
    list = next;
  }
}

绘图功能是

void drawAsteroid(void *asteroid){
    Asteroid *newAsteroid = (Asteroid *)asteroid;
    printf("%d\n", newAsteroid->xPos);
    circleRGBA(renderer, newAsteroid->xPos, newAsteroid->yPos, newAsteroid->r, 0, 255, 0, 255);
}

结构定义如下

typedef struct asteroid{
    int xSpeed;
    int ySpeed;

    int xPos;
    int yPos;

    int r;
}Asteroid;

运行此代码时，我看不到屏幕上的任何东西

When i run this code i dont see anything drawn to the screen

推荐答案

GList函数不会不复制数据.如果将Asteroid结构放在堆栈上，并且超出范围，则list->data指针将指向垃圾.

The GList functions do not copy the data. If you place the Asteroid structure on the stack, and it goes out of scope, then the list->data pointer will point to garbage.

您需要在堆上分配数据，然后记住在不再需要时将其释放.

You need to allocate the data on the heap, and then remember to free it when not needed any more.

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