处理c ++中的文件映射

Question

我需要同时写一堆文件,所以我决定使用map <string, ofstream>.

map<string, ofstream> MyFileMap; 

我拿了一个vector<string> FileInd,包括,说"a" "b" "c",并尝试打开我的文件:

for (vector<string>::iterator it = FileInd.begin(); iter != FileInd.end(); ++it){
    ...
    MyFileMap[*it].open("/myhomefolder/"+(*it)+".");
}

我收到了错误

request for member 'open' in ..... , which is of non-class type 'std::ofstream*'

我试过切换到

map<string, ofstream*> MyFileMap;

但它也没有用.

有人可以帮忙吗？

谢谢.

澄清:

我试过了两个

map<string, ofstream> MyFileMap; map<string, ofstream*> MyFileMap;

既

.open ->open

4种变体都不起作用.

解决方案(在Rob的代码中建议):

基本上,我忘了"新",以下为我工作:

map<string, ofstream*> MyFileMap;
MyFileMap[*it] = new ofstream("/myhomefolder/"+(*it)+".");

Answer 1

std::map<std::string, std::ofstream>不可能工作,因为std::map要求其数据类型为可分配,而std::ofstream不是.在替代方案中,数据类型必须是指向ofstream的指针 - 原始指针或智能指针.

以下是我将如何使用C++ 11的功能:

#include <string>
#include <map>
#include <fstream>
#include <iostream>
#include <vector>

int main (int ac, char **av)
{
  // Convenient access to argument array
  std::vector<std::string> fileNames(av+1, av+ac);

  // If I were smart, this would be std::shared_ptr or something
  std::map<std::string, std::ofstream*> fileMap;

  // Open all of the files
  for(auto& fileName : fileNames) {
    fileMap[fileName] = new std::ofstream("/tmp/xxx/"+fileName+".txt");
    if(!fileMap[fileName] || !*fileMap[fileName])
      perror(fileName.c_str());
  }

  // Write some data to all of the files
  for(auto& pair : fileMap) {
    *pair.second << "Hello, world\n";
  }

  // Close all of the files
  // If I had used std::shared_ptr, I could skip this step
  for(auto& pair : fileMap) {
    delete pair.second;
    pair.second = 0;
  }
}

和第二节,在C++ 03中:

#include <string>
#include <map>
#include <fstream>
#include <iostream>
#include <vector>

int main (int ac, char **av)
{
  typedef std::map<std::string, std::ofstream*> Map;
  typedef Map::iterator Iterator;

  Map fileMap;

  // Open all of the files
  std::string xxx("/tmp/xxx/");
  while(av++,--ac) {
    fileMap[*av] = new std::ofstream( (xxx+*av+".txt").c_str() );
    if(!fileMap[*av] || !*fileMap[*av])
      perror(*av);
  }

  // Write some data to all of the files
  for(Iterator it = fileMap.begin(); it != fileMap.end(); ++it) {
    *(it->second) << "Hello, world\n";
  }

  // Close all of the files
  for(Iterator it = fileMap.begin(); it != fileMap.end(); ++it) {
    delete it->second;
    it->second = 0;
  }
}