Re: "Type-safe" sprintf

From:

"Larry Smith" <no_spam@_nospam.com>

Newsgroups:

microsoft.public.vc.language

Date:

Thu, 8 Mar 2007 20:59:02 -0500

Message-ID:

<eP12H6eYHHA.1216@TK2MSFTNGP03.phx.gbl>

This is a multi-part message in MIME format.

------=_NextPart_000_0221_01C761C4.9EFEEE20
Content-Type: text/plain;
    charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

Try this instead (much cleaner - see examples below):

#include <string>
#include <sstream>
#include <tchar.h>

// TCHAR versions of "std::string", etc.
typedef std::basic_string<TCHAR> tstring;
typedef std::basic_ostringstream<TCHAR> tostringstream;

/////////////////////////////////////////////////////////////////////////=
////
// "FormatStr" class. Use this class to format a "tstring" on the fly =
with
// streaming arguments. It's basically the C++ answer to "sprintf()" =
style
// argument lists. Instead of passing a format string and variable =
number
// of arguments however, just construct a temporary as seen in the =
examples
// below and stream the same arguments you would normally pass to any
// "std::ostream" object via the << operator. The result can then be
// implicitly converted to a "tstring" via the "tstring()" operator so
// you can effectively use it wherever you would use a "tstring" =
(frequently
// as a "const tstring &" argument for instance - see example 2 below).
//
// Example 1
// ---------
//
// // Results in "Bill Gates is worth 50 billion dollars"
// tstring String = FormatStr() << _T("Bill Gates is worth ") << 50 =
<< _T(" billion dollars");
//
// Example 2 (as above but pass to a function on the fly)
// ---------
//
// void YourFunc(const tstring &String)
// {
// // ...
// }
//
// YourFunc(FormatStr() << _T("Bill Gates is worth ") << 50 << _T(" =
billion dollars");
//
/////////////////////////////////////////////////////////////////////////=
////
class FormatStr
{
public:
    ////////////////////////////////////////////
    // IMPORTANT: Don't make T a reference arg
    // under VC6 (unfortunately). Some later
    // versions of VC6 have a bug and will
    // choke on it (infamous "internal compiler"
    // error).
    ////////////////////////////////////////////
    template <typename T>
    FormatStr &operator<<(const T &Whatever)
    {
        m_Stream << Whatever;
        return *this;
    }

    operator tstring() const
    {
        return m_Stream.str();
    }

private:
    tostringstream m_Stream;
};
------=_NextPart_000_0221_01C761C4.9EFEEE20
Content-Type: text/html;
    charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=Content-Type content="text/html; =
charset=iso-8859-1">
<META content="MSHTML 6.00.2900.3059" name=GENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY>
<DIV><FONT face="Courier New" size=2>Try this instead =
(much cleaner - see
examples below):</FONT></DIV>
<DIV><FONT face="Courier New" size=2></FONT> </DIV>
<DIV><FONT face="Courier New" size=2>#include =
<string><BR>#include
<sstream><BR>#include <tchar.h></FONT></DIV>
<DIV><FONT face="Courier New" size=2></FONT> </DIV>
<DIV><FONT face="Courier New" size=2>// TCHAR versions of =
"std::string",
etc.<BR>typedef std::basic_string<TCHAR> tstring;<BR>typedef
std::basic_ostringstream<TCHAR> tostringstream;</FONT></DIV>
<DIV><FONT face="Courier New" size=2></FONT> </DIV>
<DIV><FONT face="Courier New"
size=2>////////////////////////////////////////////////////////////////=
/////////////<BR>//
"FormatStr" class. Use this class to format a "tstring" on the fly =
with<BR>//
streaming arguments. It's basically the C++ answer to "sprintf()" =
style<BR>//
argument lists. Instead of passing a format string and variable =
number<BR>// of
arguments however, just construct a temporary as seen in the =
examples<BR>//
below and stream the same arguments you would normally pass to any<BR>// =

"std::ostream" object via the << operator. The result can then =
be<BR>//
implicitly converted to a "tstring" via the "tstring()" operator =
so<BR>// you
can effectively use it wherever you would use a "tstring" =
(frequently<BR>// as a
"const tstring &" argument for instance - see example 2 =
below).<BR>//<BR>//
Example 1<BR>// ---------<BR>//<BR>//   // Results in "Bill =
Gates is
worth 50 billion dollars"<BR>//   tstring String = =
FormatStr()
<< _T("Bill Gates is worth ") << 50 << _T(" billion
dollars");<BR>//<BR>// Example 2 (as above but pass to a function on the =

fly)<BR>// ---------<BR>//<BR>//   void YourFunc(const tstring =

&String)<BR>//   =
{<BR>//       //
....<BR>//   }<BR>//<BR>//   YourFunc(FormatStr() =
<<
_T("Bill Gates is worth ") << 50 << _T(" billion
dollars");<BR>//<BR>/////////////////////////////////////////////////////=
////////////////////////<BR>class
FormatStr<BR>{<BR>public:<BR>   
////////////////////////////////////////////<BR>    // =
IMPORTANT:
Don't make T a reference arg<BR>    // under VC6 =
(unfortunately).
Some later<BR>    // versions of VC6 have a bug and
will<BR>    // choke on it (infamous "internal
compiler"<BR>    // error).<BR>   
////////////////////////////////////////////<BR>    =
template
<typename T><BR>    FormatStr =
&operator<<(const T
&Whatever)<BR>   
{<BR>        m_Stream <<
Whatever;<BR>        return
*this;<BR>    }</FONT></DIV>
<DIV><FONT face="Courier New" size=2></FONT> </DIV>
<DIV><FONT face="Courier New" size=2>    operator =
tstring()
const<BR>    =
{<BR>       
return m_Stream.str();<BR>    }</FONT></DIV>
<DIV><FONT face="Courier New" size=2></FONT> </DIV>
<DIV><FONT face="Courier New" size=2>private:<BR>   
tostringstream m_Stream;<BR>};</FONT></DIV></BODY></HTML>

------=_NextPart_000_0221_01C761C4.9EFEEE20--