copy from QStringList to QString

[K-Str]

Hi,
since some days I try to copy one element of a QStrinList to a QList value.

QTS = QTSL[0];

Where

• QTS is a simple QTString
• list itemQTSL[0] is an element of QTStringList

But in this way it doesn't work.
I get an error:
The inferior stopped because it received a signal from the operating system.

Signal name :
SIGSEGV
Signal meaning :
Segmentation fault

I think a solution is quiete simple.
Please could someone help me?
Thanks!

[khryleption]

Hi,
Maybe your list is empty, do you check the list size ?

[K-Str]

Hi khryleption ,
thanks for your answer.
The list is not empty and in the elemnt QTSL[0] are also some data.
qDebug << QTSL[0] shows the expected content.

[K-Str]

Hi,
is it possible that the QString item QTS in uninitialized.
If yes how can I solve this?

[Pablo J. Rogina]

@K-Str said in copy from QStringList to QString:

is it possible that the QString item QTS in uninitialized.

could you please show a more complete code snippet of what you have so far?

[K-Str]

@Pablo-J-Rogina said in copy from QStringList to QString:

could you please show a more complete code snippet of what you have so far?

Hi Pablo J. Rogina,
thanks for your answer,
I think there is something wrong by using memset .

void ClassSqlite::conv_tm_to_time_t()
{
    char buffer1[80];
    QString qs;
    time_t rawtime_akt, rawtime_neu;
    struct tm * timeinfo_akt, timeinfo_neu;
    qDebug() << CSVliste.size();
    qDebug() << qs.size();
    qs = CSVliste[0];
    memset (&timeinfo_akt, 0, sizeof(struct tm));  <<<==== this statement overwites qs
    time (&rawtime_akt);
    timeinfo_akt = localtime (&rawtime_akt);
    strftime (buffer1,80,"%H:%M:%S",timeinfo_akt);
    Uhrzeit = buffer1;
    strftime (buffer1,80,"%e.%m.%Y", timeinfo_akt);
    Datum = buffer1;
    memset (&timeinfo_neu, 0, sizeof(struct tm));
    strptime(qs.toStdString().c_str(), "%d-%m-%Y %H:%M:%S", &timeinfo_neu);
//    rawtime_neu=mktime(&timeinfo_neu);
//    qDebug() << "Der unteschied ist: " << (float)rawtime_akt-(float)rawtime_neu;
}

Is there a way around tihs?

[JonB]

@K-Str said in copy from QStringList to QString:

struct tm * timeinfo_akt, timeinfo_neu;

memset (&timeinfo_akt, 0, sizeof(struct tm));  <<<==== this statement overwites qs

timeinfo_akt is just a pointer-size. This overwrites the stack. You meant

struct tm timeinfo_akt, timeinfo_neu;

You should not be using any of this code in Qt/nowadays. Seriously.

[SGaist]

Hi,

Would it not be simpler to use QDateTime ?

[K-Str]

Hi SGaist,
thanks for your answer.
I tried to use QDAteTime in the following way:

#include <QCoreApplication>
#include <QDebug>
#include <QString>
#include <QDateTime>

#include <string>

using namespace std;

bool TimeCheck()
{
    QString QS_OldTime = "2020-08-20 09:48:33";
    QString QS_Format = "yyyy-MM-dd hh:mm.ss";
    QDateTime QD_OldTime, QD_AktTime;
    QD_AktTime = QDateTime::currentDateTime();
    QD_OldTime = QDateTime::fromString(QS_OldTime, QS_Format);
    return true;
}


int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    if (TimeCheck())
    {
        qDebug() << "OK";
    }
    else
    {
        qDebug() << "NOK";
    }
    return a.exec();
}

This little code should be used to check the difference betweem the aktual time and the old time
But i'm quiete confused because I do not get the expected results:

• The values the values for
  actual date and time : QDateTime(2020-08-20 12:19:19.182 CEST Qt::TimeSpec(LocalTime))
  Old date and time : QDateTime( Qt::TimeSpec(LocalTime))

• How can I get values where I can check easily how the difference is in seconds.

Whats wrong with the statement

QD_OldTime = QDateTime::fromString(QS_OldTime, QS_Format);

[J.Hilk]

@K-Str
do you spot the difference in format to actual text?

09:48:33
hh:mm.ss

[K-Str]

hi J.Hilk.
thanks for your answer!
yes but it would be better to have it in seconds like 900 seconds for 15 minutes.

[J.Hilk]

@K-Str what do you want in seconds, from what starting point/time

[K-Str]

Hi j.Hilk,
If it is possibel to get something like from time_t mode.

[J.Hilk]

@K-Str
https://doc.qt.io/qt-5/qdatetime.html#toSecsSinceEpoch

[K-Str]

J.Hilk,
thanks a lot for this tip.
It works perfect.
But how can I get the milliseconds since a given time like

    QString QS_OldTime = "2020-08-20 09:48:33";

This staement

    QD_OldTime = QDateTime::fromString(QS_OldTime, QS_Format);

doesn't work correctly

[J.Hilk]

@K-Str

This statement
QD_OldTime = QDateTime::fromString(QS_OldTime, QS_Format);
doesn't work correctly

it doesn't work correctly because your QS_Format is wrong, like I posted previously

But how can I get the milliseconds since a given

https://doc.qt.io/qt-5/qdatetime.html#msecsTo

[K-Str]

Hi j.Hilk,
ok the part

    QT_Akt=QDateTime::currentMSecsSinceEpoch();

works perfect!
But what about this part?

    QString QS_OldTime = "2020-08-15 09:48:33";
    QString QS_Format = "yyyy-MM-dd hh:mm.ss";
    QDateTime QD_OldTime, QD_AktTime;
    QD_OldTime = QDateTime::fromString(QS_OldTime, QS_Format);

I saw the value of QD_OldTime is not correctly assigned
There was a "." in

QString QS_Format = "yyyy-MM-dd hh:mm.ss";

on the place ":mm.ss"
Now it works perfect.
Thanks a lot!

[JonB]

@K-Str
Just to say: I was the peson who said you should not be using your old C code with memcpy() etc. Your new code with QString, QDateTime looks a lot neater and more C++, well done! :)

[KroMignon]

@K-Str said in copy from QStringList to QString:

But what about this part?
QString QS_OldTime = "2020-08-15 09:48:33";
QString QS_Format = "yyyy-MM-dd hh:mm.ss";
QDateTime QD_OldTime, QD_AktTime;
QD_OldTime = QDateTime::fromString(QS_OldTime, QS_Format);

This can NOT work because the pattern are not matching.
You have to change QS_OldTime or QS_Format.
Read carefully and you will see your typo ;)