[Interest] Converting std::string.c_str() code to use QString methods

[Michael Jackson]

On Aug 30, 2013, at 11:42 PM, Thiago Macieira <thiago.macieira at intel.com> wrote:

> On sexta-feira, 30 de agosto de 2013 19:47:48, Syam wrote:
>> On 31-Aug-2013 6:28 AM, "Thiago Macieira" <thiago.macieira at intel.com> wrote:
>>> On sexta-feira, 30 de agosto de 2013 19:17:58, Scott Aron Bloom wrote:
>>>> I use toUtf8()... Though it wouldn't surprise me if Thiago scolds me
>>>> for it
>>> 
>>> If you're on Unix, that's fine. It's fine because if your Unix system
>>> uses a
>>> locale different from UTF-8, you *really* should be scolded :-)
>> 
>> On Linux, whenever I need a const char* from a QString, I always do
>> toLatin1().constData().
>> 
>> Earlier I used toAscii(), but then some discussion on Qt5 suggested that
>> toLatin1() is more appropriate.
> 
> toAscii() and toLatin1() are most often the same. Except when they aren't -- 
> that's when someone called setCodecForCStrings. And then toAscii() is no 
> longer doing ASCII, it's doing something potentially incompatible with ASCII.
> 
> That's why this function is deprecated in Qt 5. In Qt 5, it's documented to do 
> US-ASCII only and it has undefined behaviour if the QString contains characters 
> not encodable in US-ASCII.
> 
>> Am I right here? Of course, the assumption is that the original QString is
>> simple English text.
> 
> Even “simple English” may contain characters not encodable in Latin 1…
> 
> As I've just proven :-)
> 
> -- 
> Thiago Macieira - thiago.macieira (AT) intel.com
>  Software Architect - Intel Open Source Technology Center

As the original poster, thanks everyone for their input. Let me add some more context to where these "strings" maybe coming from.

1) We have constants defined in headers using US ASCII Only Characters such as the following:
    const QString VoxelData("VoxelData");
    const QString H5DataContainerPath("/DataContainer/VoxelDataContainer");

2) We can get Strings from a user interface widget such as a QTextField which can be something they type in or gotten from a Open/Save File Dialog box.

3) We use the HDF5 (www.hdfgroup.org) to store files. The entire interface is "C" and uses char* to get strings into and out the file when needed. Of all the discussion going on this is the part that worries me the most. Do I use "toAscii().data()" or toLatin().data()? We are still using Qt 4.8.4 but in the next year will probably move to Qt 5. I don't want to rewrite 500 source files with APIs that are going to be deprecated in what we move up to. I'd only like to do this transition once.


Basically I am would really like to go "All In" with Qt so our programmers can have a consistent set of APIs to use at all levels of the codes. Not what we have now which is a mix of STL & Qt and MFC (in rare cases).

And not to hijack my own thread but we used std::stringstream in lots of places to build up error messages and progress messages. I started replacing all of that with QTextStream backed by a QString. Is this the right move or should I just have used QString and its various append methods?

Thanks
Mike Jackson
www.github.com/dream3d/DREAM3D