Question

我有一个结构调用Client，以及一个创建这种结构的函数myList:Array<any>=[{prop:someValue},{prop:someOtherValue}];。

现在我想实现一个创建此结构initClient的函数，但我无法弄清楚返回数据的正确语法。是table[20000]还是Client**？... 这是我的代码：Client[]：

client.h

和main.c：

 struct sClient
 {
     int num_tel;
     int nbr_appel;
     int cout;
  };

  typedef struct sClient Client;
  Client * initClient(int num_tel, int nbr_appel,int cout);
  Client *createData();

Answer 1

根据评论中讨论的内容（并考虑到我提供了一些可能令人困惑的提示），我想展示我认为符合所有要求的（唯一）解决方案：

#include <stdio.h>
#include <stdlib.h>

typedef struct { int num_tel, nbr_appel, cout; } Client;

Client* initClient(int num_tel, int nbr_appel, int cout);
Client* createData();

#define NBCLIENT 20

Client* initClient(int num_tel, int nbr_appel, int cout)
{
  Client *pClient = malloc(sizeof (Client));
  /** @bug check for NULL pointer missing! */
  pClient->num_tel = num_tel;
  pClient->nbr_appel = nbr_appel;
  pClient->cout = cout;
  return pClient;
}

Client* createData()
{
  Client *clients = malloc(NBCLIENT * sizeof (Client));
  /** @bug check for NULL pointer missing! */
  for (int i = 0; i < NBCLIENT; ++i) {
    int numeroTel = 600000000 + (rand() % NBCLIENT);
    int prixAppel = (rand() % 400) + 1;
    Client *pClient = initClient(numeroTel,1,prixAppel);
    /* copy returned CONTENTS to malloc-ed array element */
    clients[i] = *pClient; /* assignment for struct-s is granted */
    /* release pClient to prevent memory leaks - it's not anymore needed */
    free(pClient);
  }
  return clients;
}

int main()
{
  Client *clients = createData();
  for (int i = 0; i < NBCLIENT; ++i) {
    Client *pClient = clients + i; /* or: &clients[i] would work as well */
    printf("%2d.: %d, %d, %d\n",
      i, pClient->num_tel, pClient->nbr_appel, pClient->cout);
  }
  free(clients);
  return 0;
}

因此，为了匹配所需的签名，struct的返回initClient()值将被复制到malloc()中的createData()中。正如这样做，free()对于防止内存泄漏非常重要，因为malloc()中initClient()完成的内存既不会被使用也不会被引用。

在ideone上进行编译和测试。输出是：

 0.: 600000003, 1, 87
 1.: 600000017, 1, 116
 2.: 600000013, 1, 336
 3.: 600000006, 1, 93
 4.: 600000009, 1, 222
 5.: 600000002, 1, 28
 6.: 600000010, 1, 60
 7.: 600000003, 1, 327
 8.: 600000000, 1, 227
 9.: 600000012, 1, 137
10.: 600000011, 1, 169
11.: 600000007, 1, 30
12.: 600000002, 1, 331
13.: 600000002, 1, 324
14.: 600000007, 1, 336
15.: 600000009, 1, 203
16.: 600000002, 1, 259
17.: 600000009, 1, 168
18.: 600000013, 1, 57
19.: 600000011, 1, 43

initClient()中分配的临时内存和createData()中的free-d将会让我感到烦恼。只需略微更改initClient()：

的签名即可防止这种情况

#include <stdio.h>
#include <stdlib.h>

typedef struct { int num_tel, nbr_appel, cout; } Client;

void initClient(Client *pClient, int num_tel, int nbr_appel, int cout);
Client* createData();

#define NBCLIENT 20

void initClient(Client *pClient, int num_tel, int nbr_appel, int cout)
{
  pClient->num_tel = num_tel;
  pClient->nbr_appel = nbr_appel;
  pClient->cout = cout;
}

Client* createData()
{
  Client *clients = malloc(NBCLIENT * sizeof (Client));
  /** @bug check for NULL pointer missing! */
  for (int i = 0; i < NBCLIENT; ++i) {
    int numeroTel = 600000000 + (rand() % NBCLIENT);
    int prixAppel = (rand() % 400) + 1;
    initClient(clients + i, numeroTel, 1, prixAppel); 
    /* &clients[i] would've worked as well as clients + i */
  }
  return clients;
}

int main()
{
  Client *clients = createData();
  for (int i = 0; i < NBCLIENT; ++i) {
    Client *pClient = clients + i; /* or: &clients[i] would work as well */
    printf("%2d.: %d, %d, %d\n",
      i, pClient->num_tel, pClient->nbr_appel, pClient->cout);
  }
  free(clients);
  return 0;
}

在ideone上再次进行编译和测试。输出是：

 0.: 600000003, 1, 87
 1.: 600000017, 1, 116
 2.: 600000013, 1, 336
 3.: 600000006, 1, 93
 4.: 600000009, 1, 222
 5.: 600000002, 1, 28
 6.: 600000010, 1, 60
 7.: 600000003, 1, 327
 8.: 600000000, 1, 227
 9.: 600000012, 1, 137
10.: 600000011, 1, 169
11.: 600000007, 1, 30
12.: 600000002, 1, 331
13.: 600000002, 1, 324
14.: 600000007, 1, 336
15.: 600000009, 1, 203
16.: 600000002, 1, 259
17.: 600000009, 1, 168
18.: 600000013, 1, 57
19.: 600000011, 1, 43

一个在C中返回struct表的函数

1 个答案: