I have QMap<QString, MyClass*>. I need to sort it by key using natural comparison. I do:
std::map<QString, MyClass*> map = c.toStdMap();
std::sort(map.begin(), map.end(), strnatcmp1<std::pair<QString, MyClass*>>);
However, this does not even compile. And even if it did, as far as I understand, it would sort a copy of my original QMap.
Is there any way to sort my QMap by key with the function for comparison keys provided?
You have several appoaches that you could take:
Store the keys as integers after converting QString to an integer.
You can use the compare class for std::map as per the example:
You can try to use specialize this template function that QMap uses for the comparison.
#include <QMap>
#include <QDebug>
#include <map>
struct str_num_compare {
bool operator() (const QString& lhs, const QString& rhs) const
{return lhs.toInt()<rhs.toInt();}
};
int main()
{
QStringList stringList{"1", "10", "11", "2", "3", "4"};
QMap<int, QString> map;
foreach (const QString &string, stringList)
map.insert(string.toInt(), string);
qDebug() << "Integer key approach:" << map;
std::map<QString, QString, str_num_compare> std_map;
foreach (const QString &string, stringList)
std_map[string] = string;
qDebug() << "QString key approach with std::map:";
for (auto item : std_map)
qDebug() << item.first;
return 0;
}
TEMPLATE = app
TARGET = main
QT = core
CONFIG += c++11
SOURCES += main.cpp
qmake && make && ./main
Integer key approach: QMap((1, "1")(2, "2")(3, "3")(4, "4")(10, "10")(11, "11"))
QString key approach:
"1"
"2"
"3"
"4"
"10"
"11"
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