How to implement operator<() for QMap

[learning_qt]

I hope to use QMap as template
QMap<ClassA, ClassB> localMap;

class ClassA
{
public:
    setIndex(int index);
    setFlag(bool flag);
    checkIndex();
    checkFlag();
private:
    int index;
    bool flag;
};

class ClassA
{
public:
    setIndex(int index);
    setFlag(bool flag);
    checkIndex();
    checkFlag();
private:
    int index;
    bool flag;
};

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In order to use "Key" in QMap, I have to implement operator<(). But I do not know how to do it. Please help me:

}

[jpn]

There is an example in QMap docs.

[learning_qt]

I implemented by referring to the example in QMap doc. but it does not work properly. When I try to access the elements in QMap template, there were still some errors caused by operator<()

[caduel]

so, why don't you show use how you tried to implement a "less than" operation for ClassA?

[learning_qt]

void ClassA::setKey(int key)
{
    index = key;
}
 
void  ClassA::setFlag(bool status)
{
    flag= status;
}
 
int ClassA::checkKey() const
{
    return index;
}
 
bool ClassA::checkFlag() const
{
    return flag;
}
 
 
bool ClassA::operator<(const ClassA &i1)
 {
     if (index != i1.checkKey())
         return index < i1.chekcKey();
     return false;
 }

void ClassA::setKey(int key)
{
    index = key;
}

void  ClassA::setFlag(bool status)
{
    flag= status;
}

int ClassA::checkKey() const
{
    return index;
}

bool ClassA::checkFlag() const
{
    return flag;
}


bool ClassA::operator<(const ClassA &i1)
 {
     if (index != i1.checkKey())
         return index < i1.chekcKey();
     return false;
 }

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[wysota]

I'd say the operator has to be const.

[caduel]

And even if it would not have to be: it should be const.
Besides, that function is equivalent to:

bool ClassA::operator<(const ClassA &i1) const
{
   return index < i1.index;
}

bool ClassA::operator<(const ClassA &i1) const
{
   return index < i1.index;
}

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