eg:
QFile f("/home/umanga/Desktop/image.jpg");
How I get only the filename - "image.jpg"?
Use a QFileInfo to strip out the path (if any):
QFileInfo fileInfo(f.fileName());
QString filename(fileInfo.fileName());
One approach, not necessarily the best: from a QFile, you can get the file specification with QFile::fileName():
QFile f("/home/umanga/Desktop/image.jpg");
QString str = f.fileName();
then you can just use the string features like QString::split:
QStringList parts = str.split("/");
QString lastBit = parts.at(parts.size()-1);
just in addition: to seperate filename and file path having QFile f
QString path = f.fileName();
QString file = path.section("/",-1,-1);
QString dir = path.section("/",0,-2);
you don't need to create an additional fileInfo.
I use this:
bool utes::pathsplit(QString source,QString *path,QString *filename)
{
QString fn;
int index;
if (source == "") return(false);
fn = source.section("/", -1, -1);
if (fn == "") return(false);
index = source.indexOf(fn);
if (index == -1) return(false);
*path = source.mid(0,index);
*filename = fn;
return(true);
}
Related
I have a function defined and used as this:
// usage:
QMap<QString, QString> map = ...;
foo(map);
// defination:
QString stringMapToJson(const QMap<QString, QString>& arg) {
QVariant v = QVariant::fromValue(arg);
JsonDocument doc = QJsonDocument::fromVariant(v);
...
}
Then I realized v is empty.
Is there a method to convert QMap<String, QString> to QMap<String, QVariant>, so above v could be valid?
Why above v is empty? I read people were saying QVariant and qMetaData, I don't understand given the following valid, why QString have a qMetaData problem:
QString s = "";
QVariant v = s;
(A Java programmer starts her pleasant C++ journey.)
Thanks.
There are 2 ways to do this. The first is to convert your map to a QMap<QString, QVariant> like you mentioned:
QByteArray stringMapToJson1(const QMap<QString, QString>& arg)
{
QVariantMap vmap;
for(auto it = arg.cbegin(); it != arg.cend(); ++it)
{
vmap.insert(it.key(), it.value());
}
const QVariant v = QVariant::fromValue(vmap);
const QJsonDocument doc = QJsonDocument::fromVariant(v);
return doc.toJson();
}
Alternatively, you can build the json object directly from the map. In this case it's the same amount of code:
QByteArray stringMapToJson2(const QMap<QString, QString>& arg)
{
QJsonObject jObj;
for(auto it = arg.cbegin(); it != arg.cend(); ++it)
{
jObj.insert(it.key(), it.value());
}
QJsonDocument doc;
doc.setObject(jObj);
return doc.toJson();
}
This seems like a stylistic choice and I am unsure which would be faster. Both produce the same output.
One thing to note: The conversion from QString to QVariant is predefined in Qt, so the first method works fine. For objects of your own classes you would have to register that type and provide a suitable conversion which can be a bit tough to get right. In the second method you could do this conversion inline in the loop.
Hi I tried to write my own version of memmove and I find the following code resulting in a segmentation fault. It would be great if someone could help me figure out why this behavior would occur!
However, when I use something like:
char source[20] = "Hello, this is Piranava", the code works fine!
void *memmoveLocal(void *dest, const void *src, unsigned int n)
{
char *destL = dest;
const char *srcL = src;
int i = 0;
if(dest == NULL || src == NULL)
{
return NULL;
}
else
{
// if dest comes before source, even if there's an overlap, we should move forward
// because if there's an overlap (when dest < src) and we move backward, we'd overwrite the overlapping bytes in src
if(destL < srcL)
{
printf("Forward\n");
while(i < n)
{
destL[i] = srcL[i];
i++;
}
}
else // in all other cases (even if there's overlap or no overlap, we can move backward)
{
printf("Backward\n");
i = n - 1;
while(i >= 0)
{
destL[i] = srcL[i];
i--;
}
}
}
return dest;
}
void main()
{
char *source = "Hello, this is ABC";
char *destination = malloc(strlen(source)+1);
memmoveLocal(source+5, source, 5);
printf("Source: %s \nDestination: %s, size: %d\n", source, destination, strlen(destination));
}
However, if I replace
char *source = "Hello, this is ABC";
with
char source[20] = "Hello, this is ABC";
, it works fine!
memmoveLocal(source+5, source, 5);
You are trying to overwrite a string literal, which is not writable.
Did you intend to memmoveLocal(destination, source+5, 5) instead?
char source[20] = "Hello, this is ABC";
That turns source from a string literal into a char[] array initialized with a string literal. The array is writable, so your program no longer crashes.
I'm trying to parse a QString character by character with a while loop, but I can't figure out how to parse an individual character to char type. Here's my code, I know it's not optimal:
QString temp = (QString)t[0];
int i = 1;
while (t[i] != " ");
{
temp.append(t[i]);
i += 1;
}
I've seen the casting with toLocal8bit function, but whatever I try I just cannot adapt it to my code.
Qt Creator shows this error:
error: conversion from 'const char [2]' to 'QChar' is ambiguous
in line with the while function call
You can use C++ 11 range based for loop
for (auto chr : text)
{
if (!chr.isDigit()) // for exmpl.
return false;
}
Why don't you try that :
QString test = "test";
for(int i = 0; i< test.length(); i++)
{
if (test.at(i) != " ")
test.at(i).toLatin1();
}
I m trying to convert QString with special characters to const char* but I did not succeed. my function is:
void class::func(const QString& Name) // fileName = "â.tmp"
{
qDebug()<< Name; // display "â.tmp"
const char* cfileName = Name.toAscii().data();
qDebug() << cfileName; // display "a?.tmp"
}
qDebug()<< fileName display the true value that is "â.tmp" but after converting it to const a char*, I do not succeed to have the right value.
In the second time I try to use const char* cfileName = QString::fromUtf8(fileName.toAscii().data()); but I did not still have the right value, it display the same thing: "a?.tmp". How can I fix this thank you
due to convert QString to const char* :
QString str("hi lor!");
const char *s = str.toStdString().c_str();
msg.setText(QString::fromUtf8(s));
msg.exec();
EDIT: using QByteArray QString::toUtf8 () const is much better
QString string = "â.tmp";
const char* encodedString = string.toUtf8().data();
ORIGIONAL:
You probably need to use a codec, see http://qt-project.org/doc/qt-4.8/qtextcodec.html
something like this should work:
QString string = "â.tmp";
QTextCodec *codec = QTextCodec::codecForName("UTF-8");
QByteArray encodedString = codec->fromUnicode(string);
the documentation does not say what encoding types QDebug & QDebug::operator<< ( const char * s ) supports, it may be platform dependent, try verifying a correct conversion another. The problem may be in qDebug() or the stream it writes to.
I get result from db by selectall query and I want save result in array and send it by socket.
db.open();
QSqlQuery *selectall = new QSqlQuery(db);
selectall->prepare("select * from phone_table");
selectall->exec();
selectall->first();
QString result;
QByteArray arrayresult;
int index = 0;
while (selectall->next())
{
index += 1;
// qint16 id = selectall->value(0).toString();
QString name_ = selectall->value(1).toString();
QString surname = selectall->value(2).toString();
QString phone_number = selectall->value(3).toString();
result = "*"+ name_+"*"+surname+"*"+phone_number;
arrayresult[index] = result;
}
I get this error binary '=' : no operator found which takes a right-hand operand of type 'const char [16]'
You are trying to set a QByteRef to a QString.
I think you may want a QList and to arrayresult.append(result).
Or else if you want one QByteArray with the concat of all results use arrayresult+= result.
You may build the QString you want to initialize QByteArray. To then convert from QString to QByteArray, you can do
QByteArray array_ = string_.toLatin1();
if encoding is Latin1.
You may alternatively use append
QByteArray & QByteArray::append ( const QString & str )
This is an overloaded function.
Appends the string str to this byte array. The Unicode data is
converted into 8-bit characters using QString::toAscii().
If the QString contains non-ASCII Unicode characters, using this
function can lead to loss of information. You can disable this
function by defining QT_NO_CAST_TO_ASCII when you compile your
applications. You then need to call QString::toAscii() (or
QString::toLatin1() or QString::toUtf8() or QString::toLocal8Bit())
explicitly if you want to convert the data to const char *.
append is doing the same as + operator.
You can do the following with the toLatin1() function of the QString.
// ...
QString result = QString( "*%1*%2*%3" ).arg( name_ )
.arg( surname )
.arg( phone_number );
QByteArray resultArray = result.toLatin1();
// Or ...
// QByteArray resultArray = result.toLocal8Bit();
// QByteArray resultArray = result.toUtf8();
And you shall use a QList< QByteArray > for containing the results, or you can just append the last result item to your final result object.