QMap in QList | i can get value but i can`t set value

[petrusPL]

Hi
i dynamicly create a QMap and put it on QList

QMap<QPoint, int> myMap;
 
 for(int i=0; i<5; i++)
    {
        for(int j=0; j<5; j++)
        {
            myMap.insert(QPoint(j, i), 0);
        }
    }
 
this->MapList.insert(0, myMap);

QMap<QPoint, int> myMap;

 for(int i=0; i<5; i++)
    {
        for(int j=0; j<5; j++)
        {
            myMap.insert(QPoint(j, i), 0);
        }
    }

this->MapList.insert(0, myMap);

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and i can get the value but i can`t set it :C

1) this->MapList.at(0)[QPoint(x,y)]  = 1;
 
2) this->MapList.at(0).insert(QPoint(x,y), 1);

1) this->MapList.at(0)[QPoint(x,y)]  = 1;

2) this->MapList.at(0).insert(QPoint(x,y), 1);

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1) lvalue required as left operand of assignment

2)passing 'const QMap<QPoint, int>' as 'this' argument of 'QMap<Key, T>::iterator QMap<Key, T>::insert(const Key&, const T&) [with Key = QPoint; T = int]' discards qualifiers [-fpermissive]

why it dont work ?