Qt wiki will be updated on October 12th 2023 starting at 11:30 AM (EEST) and the maintenance will last around 2-3 hours. During the maintenance the site will be unavailable.

ToStdWStringAndBuiltInWchar: Difference between revisions

From Qt Wiki
Jump to navigation Jump to search
No edit summary
No edit summary
Line 1: Line 1:
'''English''' [[toStdWStringAndBuiltInWchar SimplifiedChinese|简体中文]]<br />[[Category:HowTo]]<br />[[Category:snippets]]
'''English''' [[toStdWStringAndBuiltInWchar SimplifiedChinese|简体中文]]
[[Category:HowTo]]
[[Category:snippets]]


= QString, std::wstring and built-in wchar_t =
= QString, std::wstring and built-in wchar_t =
Line 5: Line 7:
== Problem statement ==
== Problem statement ==


Qt advises to build your Qt based software without wchar_t as built-in type, just like the Qt libraries themselves. In some cases this is not desired by the environment or not possible because other libraries have been built with the built-in wchar_t type. This will cause obscure linker errors when using std::wstrings, and &quot;QString::toStdWString()&quot;:http://doc.qt.io/qt-5.0/qtcore/qstring.html#toStdWString and &quot;QString::fromStdWString()&quot;:http://doc.qt.io/qt-5.0/qtcore/qstring.html#fromStdWString.
Qt advises to build your Qt based software without wchar_t as built-in type, just like the Qt libraries themselves. In some cases this is not desired by the environment or not possible because other libraries have been built with the built-in wchar_t type. This will cause obscure linker errors when using std::wstrings, and "QString::toStdWString()":http://doc.qt.io/qt-5.0/qtcore/qstring.html#toStdWString and "QString::fromStdWString()":http://doc.qt.io/qt-5.0/qtcore/qstring.html#fromStdWString.


== Possible solution ==
== Possible solution ==
Line 11: Line 13:
Windows uses utf-16 for its character encoding, as does Qt. Using this information we can use the following code to work around the issue:
Windows uses utf-16 for its character encoding, as does Qt. Using this information we can use the following code to work around the issue:


<code>/*! Convert a QString to an std::wstring '''/<br />std::wstring qToStdWString(const QString &amp;str)<br />{<br />#ifdef _MSC_VER<br /> return std::wstring((const wchar_t''')str.utf16());<br />#else<br /> return str.toStdWString();<br />#endif<br />}
<code>/*! Convert a QString to an std::wstring */
std::wstring qToStdWString(const QString &amp;str)
{
#ifdef _MSC_VER
return std::wstring((const wchar_t''')str.utf16());
#else
return str.toStdWString();
#endif
}


/*! Convert an std::wstring to a QString '''/<br />QString stdWToQString(const std::wstring &amp;str)<br />{<br />#ifdef _MSC_VER<br /> return QString::fromUtf16((const ushort''')str.c_str());<br />#else<br /> return QString::fromStdWString(str);<br />#endif<br />}</code>
/*! Convert an std::wstring to a QString */
QString stdWToQString(const std::wstring &amp;str)
{
#ifdef _MSC_VER
return QString::fromUtf16((const ushort''')str.c_str());
#else
return QString::fromStdWString(str);
#endif
}</code>

Revision as of 10:25, 25 February 2015

English 简体中文

QString, std::wstring and built-in wchar_t

Problem statement

Qt advises to build your Qt based software without wchar_t as built-in type, just like the Qt libraries themselves. In some cases this is not desired by the environment or not possible because other libraries have been built with the built-in wchar_t type. This will cause obscure linker errors when using std::wstrings, and "QString::toStdWString()":http://doc.qt.io/qt-5.0/qtcore/qstring.html#toStdWString and "QString::fromStdWString()":http://doc.qt.io/qt-5.0/qtcore/qstring.html#fromStdWString.

Possible solution

Windows uses utf-16 for its character encoding, as does Qt. Using this information we can use the following code to work around the issue:

/*! Convert a QString to an std::wstring */
std::wstring qToStdWString(const QString &amp;str)
{
#ifdef _MSC_VER
 return std::wstring((const wchar_t''')str.utf16());
#else
 return str.toStdWString();
#endif
}

/*! Convert an std::wstring to a QString */
QString stdWToQString(const std::wstring &amp;str)
{
#ifdef _MSC_VER
 return QString::fromUtf16((const ushort''')str.c_str());
#else
 return QString::fromStdWString(str);
#endif
}