what's the difference betwwen these two ways to use std::ofstream

[thinktwice]

//case 1, works fine
function(..)
{
std::ofstream out;
out.open(file);
out << "error info" <<endl;
out.close();
}

//case 2, declare it in a class
class Logger
{
public:
Logger(std::wst ring file, std::ios_base:: openmode mode /*undefined
too, why?*/){}
private:
std::ofstream out; //error c2079, uses undefined class
'std::basic_ofs tream<_Elem, _Traits>'
}

btw, how to use ios_base:openmo de? is it declared in std namespace?

[Bo Persson]

"thinktwice " <me*********@gm ail.comskrev i meddelandet
news:11******** ************@m7 3g2000cwd.googl egroups.com...

//case 1, works fine
function(..)
{
std::ofstream out;
out.open(file);
out << "error info" <<endl;
out.close();
}

Just a guess: The function is in a cpp file that includes the
<fstreamheade r?

//case 2, declare it in a class
class Logger
{
public:
Logger(std::wst ring file, std::ios_base:: openmode mode
/*undefined
too, why?*/){}
private:
std::ofstream out; //error c2079, uses undefined class
'std::basic_ofs tream<_Elem, _Traits>'
}

A class declaration if often in a .h file. If so, it must also include
the necessary headers for names it uses.

>
btw, how to use ios_base:openmo de? is it declared in std namespace?

It is. There is a header <iosthat contains a lot of types and
constants used by the stream classes.
Bo Persson

[thinktwice]

thanks Persson , you are right,
i do include <fstreamin cpp file.
and the function implementation and the class definination is in the
header file.