使用字符串作为打开文件路径的C ++ ifstream错误

Question

I get this error when I try running the program.What might be the problem as the code is correct as far as I can see.

Here is the error

std::basic_fstream::basic_fstream(std::string&, const openmode&)'

Here is the code

#include <fstream>
#include <string>
#include <iostream>
using namespace std;

int main()
{
string fileName;
int frequencyArray[26];
char character;

for (int i = 0; i < 26; i++)
    frequencyArray[i] = 0;

cout << "Please enter the name of file: ";
getline(cin, fileName);

fstream inFile(fileName, fstream::in);  // to read the file

if (inFile.is_open())
{
    while (inFile >> noskipws >> character)
    {
        // if alphabet
        if (isalpha(character))
        {
            frequencyArray[(int)toupper(character) - 65]++;
        }
    }

    inFile.close();

    cout << "Letter frequencies are as: " << endl;
    for (int i = 0; i < 26; i++)
    {
        cout << (char)(i + 65) << " = " << frequencyArray[i] << endl;
    }
}
else
{
    cout << "Invalid File. Exiting...";
}


return 0;
}

Answer 1

You could change

fstream inFile(fileName, fstream::in); 

to

fstream inFile(fileName.c_str(), fstream::in);

Answer 2

Although C++11 defines a std::fstream constructor that accepts a std::string as input, Microsoft's implementation of std::fstream apparently does not:

https://msdn.microsoft.com/en-us/library/a33ahe62.aspx#basic_fstream__basic_fstream

You will have to use the std::string::c_str() method to pass the filename:

fstream inFile(fileName.c_str(), fstream::in);

That being said, consider using std::ifstream instead:

ifstream inFile(fileName.c_str());