C - 结构内的函数 [英] C - function inside struct

问题描述

我正在尝试在 struct 中分配一个函数，到目前为止我有这个代码:

typedef struct client_t client_t, *pno;结构体client_t{pid_t pid;字符密码[TAM_MAX]；//->50 个字符pno 下一个；pno AddClient(){/* 代码 */}};int main(){client_t 客户端；//代码 ..client.AddClient();}

<块引用>

**Error**: *client.h:24:2: error: 预期的 ‘:’, ‘,’, ‘;’, ‘}’ 或 ‘__attribute__’ 在 ‘{’ 标记之前.*

正确的做法是什么?

解决方案

它不能直接完成，但是您可以使用函数指针并显式传递this"来模拟同样的事情.参数:

typedef struct client_t client_t, *pno;结构体client_t{pid_t pid;字符密码[TAM_MAX]；//->50 个字符pno 下一个；pno (*AddClient)(client_t *);};pno client_t_AddClient(client_t *self) {/* 代码 */}int main(){client_t 客户端；client.AddClient = client_t_AddClient;//可能真的在某些 init fn 中完成//代码 ..client.AddClient(&client);}

然而，事实证明，这样做并没有真正为您带来很多好处.因此，您不会看到许多以这种方式实现的 C API，因为您也可以只调用外部函数并传递实例.

Im trying to assign a function inside a struct, so far I have this code:

typedef struct client_t client_t, *pno;
struct client_t
{
    pid_t pid;
    char password[TAM_MAX]; // -> 50 chars
    pno next;
    
    pno AddClient() 

    {
        /* code */
    }
};

int main()
{
    client_t client;

    // code ..

    client.AddClient();
}

**Error**: *client.h:24:2: error: expected ‘:’, ‘,’, ‘;’, ‘}’ or ‘__attribute__’ before ‘{’ token.*

Which is the correct way to do it ?

解决方案

It can't be done directly, but you can emulate the same thing using function pointers and explicitly passing the "this" parameter:

typedef struct client_t client_t, *pno;
struct client_t
{
    pid_t pid;
    char password[TAM_MAX]; // -> 50 chars
    pno next;

    pno (*AddClient)(client_t *); 
};

pno client_t_AddClient(client_t *self) { /* code */ }

int main()
{

    client_t client;
    client.AddClient = client_t_AddClient; // probably really done in some init fn

    //code ..

    client.AddClient(&client);

}

It turns out that doing this, however, doesn't really buy you an awful lot. As such, you won't see many C APIs implemented in this style, since you may as well just call your external function and pass the instance.

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