C语言 如何在C中创建结构的新实例
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How to create a new instance of a struct in C
提问by Robin Huang
In C, when you define a struct. What is the correct way to create a new instance? I've seen two ways:
在 C 中，当您定义结构时。创建新实例的正确方法是什么？我见过两种方式：
struct listitem {
int val;
char * def;
struct listitem * next;
};
The first way (xCode says this is redefining the struct and wrong):
第一种方式（xCode 说这是重新定义结构并且是错误的）：
struct listitem* newItem = malloc(sizeof(struct listitem));
The second way:
第二种方式：
listitem* newItem = malloc(sizeof(listitem));
Alternatively, is there another way?
或者，还有其他方法吗？
采纳答案by Robin Huang
The second way only works if you used
第二种方法仅在您使用时才有效
typedef struct listitem listitem;
before any declaration of a variable with type listitem. You can also just statically allocate the structure rather than dynamically allocating it:
在任何类型为变量的声明之前listitem。您也可以只静态分配结构而不是动态分配它：
struct listitem newItem;
The way you've demonstrated is like doing the following for every intyou want to create:
您演示的方式就像为int您要创建的每个人执行以下操作：
int *myInt = malloc(sizeof(int));
回答by Prog_is_life
It depends if you want a pointer or not.
这取决于你是否想要一个指针。
It's better to call your structure like this :
最好这样称呼您的结构：
Typedef struct s_data
{
int a;
char *b;
etc..
} t_data;
After to instanciate it for a no-pointer structure :
在将其实例化为无指针结构之后：
t_data my_struct;
my_struct.a = 8;
And if you want a pointer you need to malloc it like that :
如果你想要一个指针，你需要像这样 malloc 它：
t_data *my_struct;
my_struct = malloc(sizeof(t_data));
my_struct->a = 8
I hope this answer to your question
我希望这能回答你的问题
回答by Scott G.
struct listitem newItem; // Automatic allocation
newItem.val = 5;
Here's a quick rundown on structs: http://www.cs.usfca.edu/~wolber/SoftwareDev/C/CStructs.htm
这是结构的简要概述：http: //www.cs.usfca.edu/~wolber/SoftwareDev/C/CStructs.htm
