ofstream issue in Visual C++ 2010 regarding Strings

Question

I am trying to create a Windows Forms Application in Visual C++ 2010. I have saved some particular string in string variable "stat" like:

System::String ^stat = "sample string";

The problem is, I cannot write it to a text file using ofstream. When I try this:

if ( opstat == true ) // opstat is a bool variable
{
    ofstream outf("mytxt.txt",ios::app);
    outf << stat;
    outf.close();
}

Compiler returns an error:

error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'System::String ^' (or there is no acceptable conversion)

And a huge error that goes on forever like:

1>          D:\Development\Visual Studio 2010\VC\include\ostream(447): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(long double)'
1>          with
1>          [
1>              _Elem=char,
1>              _Traits=std::char_traits<char>
1>          ]

What am I supposed to do here?

P.S. I have already included all necessary headers (or the ones I think are necessary) like string, fstream, istream, iomanip etc.

Hmm, I assume you are using std::ostream? So what exactly is System::String? The problem seems to be that there is no "<<" operator defined in std::ostream with your "System::String" as second operand, whereas with "std::String" it would work. — user905686, Dec 19 '11 at 18:49
Are you aware of the difference between [c++](http://en.wikipedia.org/wiki/C%2B%2B) and [c++/cli](http://en.wikipedia.org/wiki/C%2B%2B_CLI)? I ask because you tagged with the former, but this code is the latter. — Benjamin Lindley, Dec 19 '11 at 18:50
@user905686: `System::String` refers to the .NET String class I think. — dreamlax, Dec 19 '11 at 18:59

jzila · Answer 1 · 2011-12-19T19:10:43.570

2

std::ofstream is an C++ Standard Library function, and it's not built to support System::String^. If you want to write to a file from a System::String^, you should use the System::IO::FileStream class. Otherwise, use a std::string instead of System::String^.

edited Dec 19 '11 at 19:10

answered Dec 19 '11 at 18:53

jzila

724
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`ofstream` is not, and never was part of the STL. The term is "The C++ Standard Library", and that also covers the parts that actually did originally come from the STL. – Benjamin Lindley Dec 19 '11 at 19:06

score 2 · Accepted Answer · edited May 23 '17 at 11:55

2

I think you have to convert System::String ^stat to std::string. See below link how to convert:

C++/CLI Converting from System::String^ to std::string

edited May 23 '17 at 11:55

Community

1
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answered Dec 19 '11 at 18:55

Sanish

1,699
1
12
21

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After learning how to convert `System::String` to `std::string`, perhaps as an exercise, implement a stream inserter that allows for type `System::String^`. – dreamlax Dec 19 '11 at 19:24

ofstream issue in Visual C++ 2010 regarding Strings

2 Answers2