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Qt-interest Archive, April 2007
about QString

Message 1 in thread

hi,all
what the para should be?
i write a c function like this: void sendProgramOpen(char *program);
and call it in qt appliction like this:

QString fileName = QFileDialog::getOpenFileName(this, "Open File", ".",
"G-Code files (*.ngc)");
 if (!fileName.isEmpty())
 {
  loadFile(fileName);
  sendProgramOpen(*???*)
 }

first , i write the para as "&fileName", the compile error is:
.\mainwindow.cpp(134) : error C2664: 'sendProgramOpen' : cannot convert
paramete
r 1 from 'QString *' to 'char *'
        Types pointed to are unrelated; conversion requires
reinterpret_cast, C-
style cast or function-style cast

then, i modify the para as &fileName.toStdString(), the error as follows:
.\mainwindow.cpp(134) : error C2039: 'toStdString' : is not a member of
'QString'

thanks in advance
regards
fengli
Message 2 in thread

Hi,

> i write a c function like this: void sendProgramOpen(char *program);

1.) Are you sure that you want to write a standard C function?
2.) Is it important to you to pass a "char *"? Why not use unicode-ready 
QString?
3.) What Qt-Version are you using?
4.) If it's Qt4, the correct members (as you can read in the docs) are 
QString::toAscii(), QString::toLocal8Bit() etc...

Regards,
Malte

--
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Message 3 in thread

hi,
i am using qt4.2.2
to be honest, the c function void sendProgramOpen(char *program) is not
written by me. it's in fact an API of some app. and i just want to call it
in my qt app.



2007/4/10, Malte Witt <malte.witt@xxxxxxxxxxxxx>:
>
> Hi,
>
> > i write a c function like this: void sendProgramOpen(char *program);
>
> 1.) Are you sure that you want to write a standard C function?
> 2.) Is it important to you to pass a "char *"? Why not use unicode-ready
> QString?
> 3.) What Qt-Version are you using?
> 4.) If it's Qt4, the correct members (as you can read in the docs) are
> QString::toAscii(), QString::toLocal8Bit() etc...
>
> Regards,
> Malte
>
> --
> To unsubscribe - send a mail to qt-interest-request@xxxxxxxxxxxxx with
> "unsubscribe" in the subject or the body.
> List archive and information: http://lists.trolltech.com/qt-interest/
>
>
Message 4 in thread

> hi,
> i am using qt4.2.2
> to be honest, the c function void sendProgramOpen(char *program) is 
> not written by me. it's in fact an API of some app. and i just want 
> to call it in my qt app.

Ahh - now it makes sense to me ;-)

Ok, you should be fine with doing something like:

QString myQString("I am the text to pass to sendProgramOpen(char * 
apWhatever)");
::sendProgramOpen(myQString.toAscii().data());

Regards,
Malte

--
 [ signature omitted ]
Message 5 in thread

*grrr*

> ::sendProgramOpen(myQString.toAscii().data());

Depending on what happens to the "char *" let me correct myself:

QByteArray arrayWithSomeLongerLastingScope = myQString.toAscii();
::sendProgramOpen(arrayWithSomeLongerLastingScope.data());

Malte

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Message 6 in thread

I use this and it works fine.

If str is declared as QString str;

Use str.toAscii().constData()

This gives pure char *.

regards,
Ashu

ååä wrote:
> hi,all
> what the para should be?
> i write a c function like this: void sendProgramOpen(char *program);
> and call it in qt appliction like this:
>  
> QString fileName = QFileDialog::getOpenFileName(this, "Open File", 
> ".", "G-Code files (*.ngc)");
>  if (!fileName.isEmpty())
>  {
>   loadFile(fileName);
>   sendProgramOpen(* _???_*)
>  }
>  
> first , i write the para as "&fileName", the compile error is:
> .\mainwindow.cpp(134) : error C2664: 'sendProgramOpen' : cannot 
> convert paramete
> r 1 from 'QString *' to 'char *'
>         Types pointed to are unrelated; conversion requires 
> reinterpret_cast, C-
> style cast or function-style cast
>  
> then, i modify the para as &fileName.toStdString(), the error as follows:
> .\mainwindow.cpp(134) : error C2039: 'toStdString' : is not a member 
> of 'QString'
>  
> thanks in advance
> regards
> fengli
>  
>  

-- 
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Message 7 in thread

Ashutosh Chakraborty wrote:
> I use this and it works fine.
> 
> If str is declared as QString str;
> 
> Use str.toAscii().constData()
> 
> This gives pure char *.

A more compact way of getting a const string is to use qPrintable().
> 
> regards,
> Ashu
> 
> ååä wrote:
>> hi,all
>> what the para should be?
>> i write a c function like this: void sendProgramOpen(char *program);
>> and call it in qt appliction like this:
>>  
>> QString fileName = QFileDialog::getOpenFileName(this, "Open File", 
>> ".", "G-Code files (*.ngc)");
>>  if (!fileName.isEmpty())
>>  {
>>   loadFile(fileName);
>>   sendProgramOpen(* _???_*)
>>  }
>>  
>> first , i write the para as "&fileName", the compile error is:
>> .\mainwindow.cpp(134) : error C2664: 'sendProgramOpen' : cannot 
>> convert paramete
>> r 1 from 'QString *' to 'char *'
>>         Types pointed to are unrelated; conversion requires 
>> reinterpret_cast, C-
>> style cast or function-style cast
>>  
>> then, i modify the para as &fileName.toStdString(), the error as follows:
>> .\mainwindow.cpp(134) : error C2039: 'toStdString' : is not a member 
>> of 'QString'
>>  
>> thanks in advance
>> regards
>> fengli
>>  
>>  
> 

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