将ifstream转换为istream [英] Convert ifstream to istream

问题描述

如何将ifstream转换为istream。我认为由于ifstream是istream的孩子，所以我应该可以这样做，但是我在执行此任务时遇到了问题。

How would one go about casting a ifstream into a istream. I figure since ifstream is a child of istream I should be able to do so but I have been having problems with such a task.

std::istream & inputStr = std::cin;
  std::ostream & outputStr = std::cout;
  if(argc == 3){
    std::fstream inputFile;
    inputFile.open(argv[1], std::fstream::in);
    if(!inputFile){
        std::cerr << "Error opening input file";
        exit(1);
    }
    inputStr = inputFile;
.....
}

推荐答案

不需要强制转换。

#include <fstream>
int main()
{
    using namespace std;
    ifstream    f;
    istream&    s   = f;
}

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