[Qt-interest] QString constructor is not overloaded to take std::string as parameter

[Nikos Chantziaras]

On 05/31/2010 11:19 PM, Bahadır Doğan wrote:
> Hello
>
> I just wonder why QString class doesn't have a constructor taking
> std::string as parameter.
>[...]
> What is the reason of that?

I guess that's because they want you to go through QByteArray and 
std::string::c_str() and std::string::data().  QString is Unicode, 
std::string is not.  Therefore, an std::string maps much better to a 
QByteArray.

For "importing" directly into a QString, the static QString::from*() 
routines should be used.

So I guess the question needs to be why QByteArray does not offer an 
std::string constructor.  Not sure.  Might have something to do with 
avoiding bloat since it's easy to use c_str() and data().  Or might have 
something to do with binary compatibility between STL-enabled and 
STL-disabled Qt builds.  I think.

Two common ways of constructing a QByteArray from an std::string:

   std::string stdStr;
   QByteArray b1(stdStr.c_str());
   QByteArray b2(stdStr.data(), stdStr.size());

The second one should be faster because it doesn't check for a 
terminating '\0' on every character, since the length is known beforehand.