C语言 如何在 ANSI C 的结构中使用枚举？
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How to use enum within a struct in ANSI C?
提问by TheDudeAbides
Following code has to be used in the main-function, but I don't know how it is used.
在main-function中必须使用以下代码，但我不知道它是如何使用的。
struct SomeItem
{
enum {MOVIE, MUSIC} itemType;
union {
struct Movie* movie;
struct Music* music;
};
};
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.
这个结构体用在带有previous/item/next 指针的动态链表中，但我不知道如何设置枚举。或者如何初始化它。
I need to know how it would look like in the main-function.
我需要知道它在主函数中的样子。
biglist.someitem = ???;
/* declaration I use */
struct Library* biglist;
more code to understand what Im trying to do.
更多代码来理解我想要做什么。
struct Library{
struct SomeItem* someitem;
struct SomeItem* previousItem;
struct SomeItem* nextItem;
};
compiler errors: C2037: left of 'someitem' specifies undefined struct/union 'library' C2065: MOVIE: undeclared identifier
编译器错误：C2037：“someitem”的左侧指定了未定义的结构/联合“库”C2065：电影：未声明的标识符
Im still a rookie on ANSI C, so dont shoot me ok ;)
我仍然是 ANSI C 的新手，所以不要对我开枪 ;)
采纳答案by JosephH
You're using pointers everywhere, so you need to use -> to reference the items.
您到处都在使用指针，因此您需要使用 -> 来引用项目。
ie. biglist->someitem->itemType = MOVIE;
IE。 biglist->someitem->itemType = MOVIE;
The below code compiles fine with gcc -Wall -strict:
下面的代码用 gcc -Wall -strict 编译得很好：
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;
}
(Though this code won't run of course, as I'm not allocating any memory for biglist and someitem!)
（虽然这段代码当然不会运行，因为我没有为 biglist 和 someitem 分配任何内存！）
回答by Tyler McHenry
biglist.someitem.itemType = MOVIE; /* or = MUSIC */
Or, if someitemis a pointer,
或者，如果someitem是一个指针，
biglist.someitem->itemType = MOVIE; /* or = MUSIC */
回答by Siddique
struct SomeItem
{
enum {MOVIE, MUSIC} itemType;
union {
struct Movie* movie;
struct Music* music;
} item;
struct SomeItem *next;
};
回答by deepseefan
You may initialize the enum in such a way biglist->someitem = MOVIE; but the compiler assigns integer values starting from 0. So: biglist->someitem=MOVIE returns 0 or biglist->someitem=MUSIC return 1
你可以这样初始化枚举 biglist->someitem = MOVIE; 但是编译器从 0 开始分配整数值。所以： biglist->someitem=MOVIE 返回 0 或 biglist->someitem=MUSIC 返回 1
check if it helps any good,
检查它是否有帮助，
