I've tried to convert using the following code:
template< unsigned int size >
static QString
TBuf82QString( const TBuf8< size > &buf )
{
return QString::fromUtf16(
reinterpret_cast<unsigned short*>(
const_cast<TUint8*>(
buf.Ptr() ) ), buf.Length() );
}
But It always returns something like ?????b.
EDIT: Changed code example
Using a template probably isn't a good solution, since it will result in a new instantiation of this block of code within your application binary, for every size of input string which is converted. Since the output type (QString) contains no compile-time constant, this means you end up with code bloat, for no gain.
A better approach would be to leverage the fact that TBuf8<N> inherits from TDesC8:
QString TBuf2QString(const TDesC8 &buf)
{
return QString::fromLocal8Bit(reinterpret_cast<const char *>(buf.Ptr()),
buf.Length());
}
TBuf<16> foo(_L("sometext"));
QString bar = TBuf2QString(foo);
TBuf8 is used for binary data or non-Unicode strings. TBuf16 is used for Unicode strings. TBuf is conditionally compiled and will always be TBuf16 as Symbian OS is natively Unicode.
Try using QString::fromLocal8Bit() with TBuf8::Ptr()
Related
I have to read numbers from line edit in Qt Creator, and then divide them by 100 and display them in a label.
The only method I know is:
QString OOP_marks = ui->lineEdit_OOP_marks_input->text();
ui->label_OOP_marks->setText(QString(OOP_marks));
But the above method cannot read numbers; it reads string. I have tried a lot but can't figure out the code for this part of the program.
You can use QString::toDouble for converting string to number. If you are planning to accept integers use QString::toInt instead. To convert number to string again QString::number is way to go.
const auto& OOP_marks = ui->lineEdit_OOP_marks_input->text();
bool isNumber; // optional
const double number = OOP_marks.toDouble(&isNumber);
const auto& result = isNumber ? QString::number(number / 100) : QString("Please enter valid number.");
ui->label_OOP_marks->setText(result);
But I suggest you to use QSpinBox or QDoubleSpinBox, instead of QLineEdit.
How about QString toInt function, and then static QString::number function?
QString OOP_marks = ui->lineEdit_OOP_marks_input->text();
int OOP_marks_val = OOP_marks.toInt();
ui->label_OOP_marks->setText(QString::number(OOP_marks_val/100));
I have custom(dynamic QString) for example something like this 123+555 and i need to get this after +.Also there can be something different then + (/,*,- etc.). My question is how to get part of string after some char.
Use the split function, which allows you to specify the separator and returns a list of the elements.
QString string("123+555");
QStringList listItems = string.split('+', QString::SkipEmptyParts);
QString finalString = listItems[1];
Alternatively, you can find by index the separating character location and use that with a call to right
Since you're usin Qt, you could try the class: QRegExp.
With such class you could write code like this:
// This code was not tested.
QRegExp rx("(\\d+)(\\+|\\-|\\*|/)(\\d+)"); // Be aware, I recommend you to read the link above in order to see how construct the proper regular expression.
int pos = rx.indexIn("23+344");
if (pos > -1) {
QString number_1 = rx.cap(1); // "23"
QString op = rx.cap(2); // "+"
QString number_2 = rx.cap(3); // "344"
// ...
}
This way you don't have to write code to check which of the characters(operators) "+, -, *, /" is present to then perform a split on the string depending on what character was found.
I am a C++ noob and I have written a method to get text file names including full-paths from a given directory. It gives a garbage value on the vector<wchar_t*> names. I used VS2010 debugger and analysed values. It looks like pointers are going out of scope. On the official C++ reference it says that push_back() copies values and seems like as I am pushing a pointer and it just copies pointers value.
static std::vector<wchar_t*> getFileNames(wchar_t* folder) // ex: c:\\textfiles\\My
{
using namespace std;
vector<wchar_t*> names;
wchar_t search_path[200];
swprintf(search_path, L"%s\\*.txt", folder); // ex: c:\\textfiles\\My\\*.txt
WIN32_FIND_DATA fd;
HANDLE hFind = FindFirstFile((wchar_t*)search_path, &fd);
if(hFind != INVALID_HANDLE_VALUE)
{
do
{
if(! (fd.dwFileAttributes == FILE_ATTRIBUTE_DIRECTORY) )
{
std::wstring fullPath(folder);
fullPath += L"\\";
fullPath += std::wstring(fd.cFileName); // cFilename has something like Info.txt
names.push_back((wchar_t*)fullPath.c_str());
}
}while(FindNextFile(hFind, &fd)); //goes out of scope and values become garbage
FindClose(hFind);
}
return names; //vector with garbage values
}
Is it possible to get wchar_t* pushed in to the vector someway, a better work around rather than dynamically allocating memory or using heap variables?
Can I get compiler warning for mistakes like this on VS2010 or any VS version(Now I only get casting warning and errors)?
swprintf might overflow the buffer.
(wchar_t*)search_path is a superfluous cast.
Never break out the big guns if you don't need them.
if(! (fd.dwFileAttributes == FILE_ATTRIBUTE_DIRECTORY) ) means you only ignore directories without interesting attributes.
fullPath += std::wstring(fd.cFileName); another superfluous cast.
names.push_back((wchar_t*)fullPath.c_str()); pushes a pointer to the internal buffer of fullpath into names, even though it will be destroyed at the end of the block.
What you should do is change the signature to
static std::vector<std::wstring> getFileNames(std::wstring folder)
Or at least
static std::vector<std::unique_ptr<wchar_t>> getFileNames(wchar_t* folder)
to take advantage of RAII and reduce the chance for errors.
In any case, you should rewrite the function, and should take advantage of the standard-library internally.
As an example, with the proper prototype:
static std::vector<std::wstring> getFileNames(std::wstring folder) {
std::vector<std::wstring> names;
WIN32_FIND_DATA fd;
HANDLE hFind = FindFirstFile((folder+L"\\*.txt").c_str(), &fd);
if(hFind == INVALID_HANDLE_VALUE)
return names;
auto lam = [](HANDLE* p){FindClose(*p);}
std::unique_ptr<HANDLE, decltype(lam)> guard(&hFind, lam);
folder += L"\\";
do {
if(! (fd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) )
names.push_back(folder+fd.cFileName);
} while(FindNextFile(hFind, &fd));
return names;
}
Ideally, you should store class objects in your vector, instead of character pointers (or wchar_t pointers). You can do it, but it requires some extra work. That's the part that you're missing.
The issue you're seeing is exactly what you describe: the character arrays that are owned by the wstring objects are being destroyed when the wstring goes out of scope. By using wstring::c_str(), you are not creating an independent copy of the character array, you're just looking at the one that it already has created for its own use.
So you need a way to keep a character array around longer. Either you could use the wstring, or you need to copy the character array into one of your own.
The minimal change would be something like this:
std::wstring fullPath(folder);
fullPath += L"\\";
fullPath += std::wstring(fd.cFileName); // cFilename has something like Info.txt
wchar_t *wsz = new wchar_t[fullPath.size() + 1];
wcsncpy(wsz, fullPath.c_str(), fullPath.size());
names.push_back(wsz);
That's enough to get your strings into the vector, but because you're using character pointers, it's also your responsibility to clean them up. So when you are done using the vector, you will need to iterate through and delete each one of them before you let the vector be destroyed.
As I mention in a comment below, it's much simpler to use a std::vector. There are libraries that can help you with the memory management parts, if you must use wchar_t*. You caould take a look at the Boost Smart Pointer library, for example.
The variable fullPath is a local variable.
It goes out of scope.
That is the reason the pointers are becoming junk.
Allocate a dynamic memory as
vector<wstring*> names;// instead of vector<wchar_t*> names;
std::wstring *fullPath = new wstring(folder);
Never store references of objects into a list if you are not aware of their scope.
I try to show a persian string in Qt:
QMessageBox msg;
QString str = "یا حسین";
msg.setText(QString::fromUtf8(str));
msg.exec();
but it shows the following error :
/home/msi/Desktop/VoMail
Project/Project/VoMail-build-desktop-Qt_4_8_1_in_PATH__System__Release/../VoMail/mainwindow.cpp:40:
error: no matching function for call to 'QString::fromUtf8(QString&)'
I want to use a string variable, and not a string directly.
How can I convert a QString variable to Utf8?
As seen here, QString::fromUtf8() does not accept an argument of type QString. You must give it a const char *, so you could rewrite it like this:
QMessageBox msg;
QString str = QString::fromUtf8("یا حسین");
msg.setText(str);
msg.exec();
its not good idea write like that
using this must be better
QString str(tr("ya hossein");
and use linguist and add persian translation file to your project http://qt-project.org/doc/qt-4.8/linguist-translators.html
and if you dont want use this, you must be sure your IDE or code editor (like qtcreator) use utf8 for saving files and just use
QString str("یا حسین");
it must be ok, i tested that so many times
I dont know a lot about C++, but I have to make work some C++ code with .NET. I try with DLLImport but I failed. So I try with C++/CLI to make kind of a wrapper.
But I'm not sure to understand everything...
This is the basic C++ H file with the function I want to export (MyFunction)
extern "C"
{
__declspec(dllexport) IplImage* MyFunction(IplImage *src, std::string* name, OneEnumerationType myEnum, bool myBool, float myFloat);
}
This is the Wrapper h code.
#include "MyFunction.h"; // the file containing the h code
#include <string>
namespace MyWrapper{
public ref class MyWrapperClass {
public:
MyWrapper(){};
IplImage^ GetMyFunction(IplImage *src, std::string^ name, OneEnumerationType myEnum, bool myBool, float myFloat);
}
This is the Wrapper cpp code.
#include "MyWrapperCode.h";
namespace MyWrapper{
IplImage^ MyWrapperClass::GetMyFunction(IplImage* src, std:string^ name, OneEnumerationType myEnum, bool myBool, float myFloat){
MyFunction(src, name, myEnum, myBool, myFloat);
}
}
These are my questions :
1) When I'm compiling, the error is "'^ : cannot use this indirection on type IplImage' and same message for type "std::string".
I have followed this logical :
ClasseNative clNat2 = *clNat; --> ClasseManagee clMan2 = *clMan;
ClasseNative &clNat3 = clNat2; --> ClasseManagee %clMan3 = clMan2;
ClasseNative *clNat4 = &clNat2; --> ClasseManagee ^clMan4 = %clMan2;
I have seen, that It was better to use System::String. I try this way but the initial function is using std::string... BTW, why is it better to change ?
2) How do I get the MyFunction IplImage result ? Thru a private member and a get I suppose but I dont know how to initialize it...
3) Tricky question. Is it possible for me to put the CLI obtains IplImage structure (from the OpenCV library) (the result of my function) inside a IplImage .NET structure, when I ll called my wrapper ? Dont know if the question is understandable...
Thanks a lot for your help.
Turning around for 3 days on this problem...
Your wrapper class needs to create a new std::string based on the content of a System::String^ parameter then pass to your native function. Otherwise you need to rewrite the function to take something else as the string input, for example a LPWSTR or LPCSTR.
You can write a ref class to have properties for all data that an IplImage would have, then pass that to your wrapper class. Your wrapper class then create an IplImage object based on the data of the ref class and pass to the native function. Reverse the data copying direction for the return value.
1) just by adding ^ you cannot change a native object to become managed, you have to create wrappers or transfer the data for example:
std::string nativeString = "my string";
String^ managedString = gcnew String(nativeString.c_str());
//now you can return it as
2) create a managed wrapper or use primitive datatype to transfer the data
3) note sure if this will help but look at Emgu.CV
try reading abit more about C++\CLI here are a few nice tutorials:
Quick C++/CLI - Learn C++/CLI in less than 10 minutes
C++/CLI for the C# programmer