Re: Write to an Edit Control with the << operator

David Wilkinson <>
Wed, 05 Sep 2007 14:23:39 -0400
<O2Qzen#7HHA.5316@TK2MSFTNGP04.phx.gbl> wrote:

Thank you so much David. This is simply amazing! Like magic... I can
recommend this piece of code to anyone!

My complete code looks like this now:
in GUI_Dlg.h I added (Outside any class)
template <typename T>
CEdit& operator << (CEdit& edit, const T& t) ;

in GUI_Dlg.cpp I added

template <typename T>
CEdit& operator << (CEdit& edit, const T& t)
    std::basic_ostringstream<TCHAR> os;
    os << t;

    // Print out the new text
    int nLength = edit.GetWindowTextLength();
    edit.SetSel(nLength, nLength);

    return edit;

And this is an example how I use it:

m_edit << "new text " << 10 << " " << 1234.5678 << "\r\n";

I wonder tough why endl doesn't work:
m_edit << std::endl; //Gives a compile error


Not quite sure about std::endl. But you don't need it.

BTW, when you write templates you should put all the code in a header
file, because the caller has to be able to see the code in order to
generate the implementation. Template functions (like inline functions)
are exempt from the one-definition rule.

AS you have done it you will find you are not able to use your template
from another .cpp file. I would suggest you put the code in a dedicated
header file (perhaps with other templates). Then you just include that
header from any implementation file.

David Wilkinson
Visual C++ MVP

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