[SOLVED] QMap:: How to remove some values from all keys

VladimirPivovar

Each key has a value.
How to remove each key value with an arbitrary sequence number

@
#include <QtCore/QCoreApplication>
#include <QMap>
#include <QString>
#include <QStringList>

int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QMap <QString,QStringList> qmapCollection;
QMap <QString,QStringList>::iterator it;
int i =0;

qmapCollection["One"].append("1");
qmapCollection["One"].append("11");
qmapCollection["One"].append("111");
qmapCollection["Two"].append("2");
qmapCollection["Two"].append("22");
qmapCollection["Two"].append("222");
qmapCollection["Three"].append("3");
qmapCollection["Three"].append("33");
qmapCollection["Three"].append("333");

return a.exec(&#41;;

}
@

I want to remove each key a second value,
not the value itself, and the ordinal value of the index [2] by all keys:
This is what should be output:

One - 1
One - 111
Two - 2
Two - 222
Three-3
Three-333

KA51O

-You can use "remove":http://qt-project.org/doc/qt-4.8/qmultimap.html#remove for that. Just check if the key has changed and if so reset an interal int iterator to 1 if this internal iterator modulo 2 is 0 you erase the entry pointed to by the QMap::iterator.-

-This would remove every second entry for a key, if you just want to remove the second value for a key just check if the int iterator is two instead of the modulo stuff.-

@
QMultiMap<QString, int>::iterator mapIt = yourMap.begin();
QString key = mapIt.key();
int it = 0;
while(mapIt != yourMap.end())
{
if(key != mapIt.key())
{
key = mapIt.key();
it = 1;
if(it % 2 == 0)
{
yourMap.remove(key,mapIt.value());
}
}
mapIt++;
it++;
}
@

-Didn't test this. This is just an idea.-

Edit: Just realized my solution was for a "QMultiMap":http://qt-project.org/doc/qt-4.8/qmultimap.html <QString, int> and not for your case QMap<QString, QStringList>

@
QMap<QString, QStringList>::iterator mapIt = yourMap.begin();
while(mapIt != yourMap.end())
{
QString key = mapIt.key();
QStringList oldValue = mapIt.value();
QStringList newValue;
for(int counter = 0; counter < oldValue.size(); counter++)
{
if(counter != 1)
{
newValue << oldValue.at(counter);
}
}
//this overwrites the old value
yourMap.insert(key,newValue);
mapIt++;
}
@

This should remove the second entry in the QStringList returned as a keys value.

VladimirPivovar

with erase() I tried, the key is removed with all the values.
In the end, get two keys instead of three.

I want every second (third, fourth) the value removed from all key

KA51O

Just updated my previous post. Sorry for the missunderstanding. Maybe you can use QMultiMap<QString, int> or QMultiMap<QString, QString> instead of QMap<QString, QStringList>. I think that might be more convenient in your case.

VladimirPivovar

Can you please give the code in relation to my case

QMap<QString,QStringlist>
QMultiMap<QString, QStringlist>

with

@
qmapCollection["One"].append("1");
qmapCollection["One"].append("11");
qmapCollection["One"].append("111");
qmapCollection["Two"].append("2");
qmapCollection["Two"].append("22");
qmapCollection["Two"].append("222");
qmapCollection["Three"].append("3");
qmapCollection["Three"].append("33");
qmapCollection["Three"].append("333");
@

twsimpson

Instead of
@QMap<QString, QStringList> qmapCollection;@

You use
@QMultiMap<QString, QString> qmapCollection;@

and insert values with:
@
qmapCollection.insert("One", "1");
qmapCollection.insert("One", "11");
//etc
@

VladimirPivovar

Thank you very much!!!

Solved!

VladimirPivovar

Full code:

@
#include <QtCore/QCoreApplication>
#include <QMap>
#include <QString>
#include <QStringList>

int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QMap <QString,QStringList> qmapCollection;
QMap<QString, QStringList>::iterator mapIt;

QString key = NULL;
QStringList oldValue ;
QStringList newValue ;

qmapCollection["One"].append("1");
qmapCollection["One"].append("11");
qmapCollection["One"].append("111");
qmapCollection["Two"].append("2");
qmapCollection["Two"].append("22");
qmapCollection["Two"].append("222");
qmapCollection["Three"].append("3");
qmapCollection["Three"].append("33");
qmapCollection["Three"].append("333");


mapIt = qmapCollection.begin();

while(mapIt != qmapCollection.end())
{
        key = mapIt.key();
        oldValue = mapIt.value();

        newValue.clear(); /// <--------------------------------

        for(int counter = 0; counter < oldValue.size(); counter++)
        {
           if(counter != 1)
           {
              newValue << oldValue.at(counter);
           }
        }


        qmapCollection.insert(key,newValue);
        mapIt++;
}

return a.exec&#40;&#41;;

}

@