CODEWITHSUNDEEP
c++codeblocks
CasualCoder
CasualCoder

Reputation: 332

Strings as File names

If I set a string as a filename, it doesn't work and I have no idea why. (I'm using codeblocks and it seems to work on other IDEs)

#include <iostream>
#include <fstream>
using namespace std;
int main()
{
   string FileName="Test.txt";
   ofstream File;
   File.open(FileName);
}

This does not work,while this next one does:

#include <iostream>
#include <fstream>
using namespace std;
int main()
{
   ofstream File;
   File.open("Test.txt");
}

Error message:

no matching function for call to std::basic_ofstream::open(std::string&)

Can someone help a bit with this problem, I cannot understand why this error occurs.

Upvotes: 0

Views: 1414

Answers (1)

Christian Hackl
Christian Hackl

Reputation: 27528

Due to what should be considered a historical accident in the early era of C++ standardisation, C++ file streams originally didn't support std::string for filename parameters, only char pointers.

That's why something like File.open(FileName), with FileName being a std::string, didn't work and had to written as File.open(FileName.c_str()).

File.open("Test.txt") always worked because of the usual array conversion rules which allow the "Test.txt" array to be treated like a pointer to its first element.

C++11 fixed the File.open(FileName) problem by adding std::string overloads.

If your compiler doesn't support C++11, then perhaps you should get a newer one. Or perhaps it does support C++11 and you just have to turn on the support with a flag like -std=c++11.

Upvotes: 6

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