如何在ANSI C的结构体中使用枚举？ [英] How to use enum within a struct in ANSI C?

问题描述

继code在主函数中使用，但我不知道如何使用它。

Following code has to be used in the main-function, but I don't know how it is used.

struct SomeItem
{
    enum {MOVIE, MUSIC} itemType;
    union {
        struct Movie* movie;
        struct Music* music;
    };
};

这是结构与previous /项目/ next指针动态链表使用，但我不知道如何设置枚举。或如何初始化。

this struct is used in a dynamic linked list with previous/item/next pointer, but I don't know how you can set the enum. Or how to initialize it.

我需要知道它会是什么样子的主要功能。

I need to know how it would look like in the main-function.

biglist.someitem = ???;
/* declaration I use */
struct Library* biglist;

更多code明白了什么我试着做。

more code to understand what Im trying to do.

struct Library{
struct SomeItem* someitem;
struct SomeItem* previousItem;
struct SomeItem* nextItem;
};

编译器错误：
C2037：的someitem左指定未定义的结构/联合图书馆
C2065：电影：未声明的标识符

compiler errors: C2037: left of 'someitem' specifies undefined struct/union 'library' C2065: MOVIE: undeclared identifier

我还在上ANSI C是菜鸟，所以不要拍我OK;）

Im still a rookie on ANSI C, so dont shoot me ok ;)

推荐答案

您正在使用指针无处不在，所以你需要使用 - >引用的项目

You're using pointers everywhere, so you need to use -> to reference the items.

IE浏览器。 biglist-＆GT; someitem-＆GT; ITEMTYPE = MOVIE;

下面code编译罚款用gcc -Wall -strict：

The below code compiles fine with gcc -Wall -strict:

struct SomeItem
{
    enum {MOVIE, MUSIC} itemType;
    union {
        struct Movie* movie;
        struct Music* music;
    } item;
};

struct Library{
   struct SomeItem* someitem;
   struct SomeItem* previousItem;
   struct SomeItem* nextItem;
};

int main(void)
{
   struct Library* biglist;

   biglist->someitem->itemType = MOVIE;

   return 0;
}

（虽然这code不会，当然跑，因为我不分配为biglist任何内存和someitem！）

(Though this code won't run of course, as I'm not allocating any memory for biglist and someitem!)

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