Question

我正在尝试学习指针，但我得到了这个错误。我是否需要更改头文件类Request？为什么我会收到这样的错误？

cannot convert `req' from type `Request' to type `Request *'

错误发生在这些行中：

//Store necessary information in a Request object for each request. 
Request req(url, request, 1);

Request *reqq = req; //req points to the object
list->Append(reqq);

代码：

void 
ClientThread(int request)
{
  const int sz = 50;
  char url[sz];

  FILE *fp = fopen("url.txt", "r");
  if (!fp)
    printf("  Cannot open file url.txt!\n");
  else {
    int pos = 0;
    char c = getc(fp);
    while (c != EOF || pos == sz - 1) {
      if (c == '\n') {
    url[pos] = '\0';
    serve(url);
    pos = 0;

    //Store necessary information in a Request object for each request. 
    Request req(url, request, 1);

    Request *reqq = req; //req points to the object
    list->Append(reqq);

      }
      else {
    url[pos++] = c;
      }
      c = getc(fp);
    }
    fclose(fp);
  }
}

我的request.h文件包含以下内容：

class Request
{
 public:
  //constructor intializes request type

  Request(char *u, int rqtID, int rqtrID);
  char *url;
  int requestID;
  int requesterID;

}

Answer 1

您需要使用此处的address-of operator：

Request *reqq = &req; //req points to the object 
// -------------^

请注意，在这种情况下& {{1}}。

如果操作数是某种类型T的左值表达式，则运算符＆amp; 创建并返回类型为T *的prvalue。

Answer 2

使用req添加&req的引用。指针类型接受指针值，而不是对象。

Request *reqq = &req; //req points to the object

键入错误和指针混淆

2 个答案: