[Qt-interest] Fwd: Convert a QString to string

[ami guru]

Hello Thiago,


What  if we are using some third party API that uses the std::string instad
of the std::wstring


The third party API has function that accept string instead


Any suggestion on that?


Regards
Sajjad

---------- Forwarded message ----------
From: Thiago Macieira <thiago.macieira at trolltech.com>
Date: Tue, Feb 10, 2009 at 4:00 PM
Subject: Re: [Qt-interest] Convert a QString to string
To: qt-interest at trolltech.com


Em Terça-feira 10 Fevereiro 2009, às 15:05:18, Jan Ekholm escreveu:
> On Tuesday 10 February 2009, Sujan Dasmahapatra wrote:
> > How can I convert a    QString  str1 to string str2.
>
> Assuming you mean std::string it's pretty obvious if you actually look
into
> the docs a bit...
>
>       std::string QString::toStdString () const

Please be careful with that function.

std::string is not a string (in the Qt sense), but a byte array. It's closer
to QByteArray than to QString. That means that, when you convert from
QString
to std::string, you're introducing an encoding conversion and you should,
therefore, be very careful.

Unlike the conversions to QByteArray, QString offers no choice of encoding
for
the conversion to std::string. Your only option is the toAscii() conversion,
which is Latin 1 by default but can be changed with
QTextCodec::setCodecForCStrings. This is important, because it's not the
locale conversion: you may be losing data by converting to std::string.

My recommendation is that you instead modify the rest of your code to use
QString, as far as you can.

If you can't, then try to use std::wstring instead: all platforms where Qt
is
supported use UTF-16 or UCS-4 for wchar_t, so there's the conversion is
trivial and there's no loss of data.

--
Thiago Macieira - thiago.macieira (AT) nokia.com
 Senior Product Manager - Nokia, Qt Software
    Sandakerveien 116, NO-0402 Oslo, Norway

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