如何初始化指向结构的指针数组？

Is it possible to initialize an array of pointers to structs? Something like:

是否可以初始化一个指向结构的指针数组？就像是：

struct country_t *countries[] = {
        {"United States of America", "America"},
        {"England", "Europe"},
        {"Ethiopia", "Africa"}  
    }

I want to do that in order to get the entities in not-contiguous memory, and the pointers to them in contiguous memory... But I can't use dynamic memory, so I wonder if it is possible without it.

我想这样做是为了让实体在不连续的内存中，并在连续的内存中指向它们......但我不能使用动态内存，所以我想知道没有它是否可行。

2 个解决方案

#1

Well, your code uses structures rather than pointers to structures. There are ways to do what you seek, including:

好吧，您的代码使用结构而不是指向结构的指针。有办法做你想要的，包括：

static struct country_t us = { "United States of America", "America" };
static struct country_t uk = { "England",                  "Europe"  };
static struct country_t et = { "Ethiopia",                 "Africa"  };

struct country_t *countries[] = { &us, &uk, &et, };

There are other ways to do it with designated initializers and compound literals in C99. Section 6.5.2.5 'Compound Literals' shows the way:

在C99中，还有其他方法可以使用指定的初始值设定项和复合文字。第6.5.2.5节“复合文字”显示方式：

struct country_t *countries[] =
{
    &(struct country_t) { "United States of America", "America" },
    &(struct country_t) { "England",                  "Europe"  },
    &(struct country_t) { "Ethiopia",                 "Africa"  },
};

The standard illustrates pointers to structures with a function call. Be aware that not all C compilers accept C99 syntax, and these compound literals were not present in C89 (aka C90).

该标准说明了具有函数调用的结构的指针。请注意，并非所有C编译器都接受C99语法，并且这些复合文字在C89（又名C90）中不存在。

Edit: Upgraded to use 2-letter ISO 3166 country codes. Also made the named structures into static variables - those symbols were not visible outside the file before (because they did not exist), and now they aren't visible outside the file after, either. I debated whether to make anything const and decided not to - but using const when you can is generally a good idea. Also, in the example, there are 3 countries in 3 continents. Were you to have multiple countries in a single continent (the norm), you might want to be able to share the continent strings. However, whether you can do that safely (or at all) depends on the details of the struct country_t (which were not given), and on whether the program is allowed to update the table (which comes back to the const-ness question).

编辑：已升级为使用2个字母的ISO 3166国家/地区代码。还将命名结构变为静态变量 - 这些符号在文件之前不可见（因为它们不存在），现在它们在文件之后也不可见。我争论是否要制作任何const并且决定不 - 但是当你可以使用const时通常是一个好主意。此外，在这个例子中，有3个大陆的3个国家。如果您在一个大洲（标准）中拥有多个国家/地区，您可能希望能够共享大陆字符串。但是，你是否可以安全地（或根本不能）这样做取决于struct country_t（未给出）的详细信息，以及是否允许程序更新表（返回到const-ness问题）。

#2

This works for me:

这对我有用：


struct country_t {
    char *fullname;
    char *shortname;
};

struct country_t countries[] = {
        {"United States of America", "America"},
        {"England", "Europe"},
        {"Ethiopia", "Africa"}
};

int main(int argc, char *argv[])
{
    return 0;
}

You could be more terse and use:

你可以更简洁并使用：


struct country_t {
    char *fullname;
    char *shortname;
} countries[] = {
        {"United States of America", "America"},
        {"England", "Europe"},
        {"Ethiopia", "Africa"}
};

int main(int argc, char *argv[])
{
    return 0;
}

Edit: I found this information at The C Book

编辑：我在The C Book找到了这个信息

#1