How to fix conversion from ‘QString*’ to non-scalar type ‘QString’ requested

Naouali

Hi guys ,
I m trying to convert const char * to QString but i get the previous error.
here's the code i m using :

@
const char * hyp ;
QString res=new QString(hyp);
return res;
@

please help me to fix it .

Thanks in advance .

EDIT: please use @-tags to use code highlighting, thanks. Gerolf

giesbert

This is standard C++, if you just want to return a QString object (not on the heap!), use the following:

@
const char * hyp ;
return QString::fromLatin1(hyp);
@

A QString is something different from QString*. new creates a new object on the heap and returns a pointer. But you used an object on the stack. As you just want to return the stirng, you can use my code. Regard, I used the fromLatin1() method, to use a defined conversion. You could also use fromAscii, from Utf8, ..., depending on the encoding of your char*.

another possibilty is:

@
const char * hyp ;
QString res(QString::fromLatin1(hyp));

return res;

@

Here I use a copy constructor which may be more efficiently than the assignment operator.

Naouali

I got another error when i try your solution .
Normally the function should return this string :go forward ten meters but i get this string: " Ê orward ten meters"

giesbert

can you please give some more code of you?
I'm sure it's the text encoding.

Naouali

Ok , let me explain how the program is working :
I m writing a speech recognizer program , using the pocketsphinx library which is writen in C language .
the result of the recognizer is the hyp variable and i want to wrap it in QString to display it in QTextEdit.

giesbert

but the hyp variable content, in which encoding is it?
This is needed to know how to convert from a char* to a QString.
char* is one byte ascii, latin1, utf8, mbcs, different encodings, all this is possible and needs to be regarded on conversion from char* to QString.

if you look at the QString docu, you see, there are many conversion functions:

QString fromAscii ( const char * str, int size = -1 )
QString fromLatin1 ( const char * str, int size = -1 )
QString fromLocal8Bit ( const char * str, int size = -1 )
QString fromRawData ( const QChar * unicode, int size )
QString fromStdString ( const std::string & str )
QString fromStdWString ( const std::wstring & str )
QString fromUcs4 ( const uint * unicode, int size = -1 )
QString fromUtf8 ( const char * str, int size = -1 )
QString fromUtf16 ( const ushort * unicode, int size = -1 )

if you go further in the docs, you see:

bq. QString converts the const char * data into Unicode using the fromAscii() function. By default, fromAscii() treats character above 128 as Latin-1 characters, but this can be changed by calling QTextCodec::setCodecForCStrings().
In all of the QString functions that take const char * parameters, the const char * is interpreted as a classic C-style '\0'-terminated string. It is legal for the const char * parameter to be 0.

you should also read: "Converting Between 8-Bit Strings and Unicode Strings":http://doc.qt.nokia.com/4.7/qstring.html#converting-between-8-bit-strings-and-unicode-strings

Naouali

Thanks the QString fromLocal8Bit did the job.