How to use QMap::remove() to delete some item?

[jedychen]

QMap<int, QString> mapCity;
mapCity.insert(1,"one");
mapCity.insert(2,"two");
...
mapCity.insert(9,"nine");
...
 
//Now, I want delete 1,2,3.
 
QMap<int, QString>::Iterator it;
for( it = mapCity.begin();  it != mapCity.end();  ++it)
{
    if( it.key() < 4 )
          mapCity.remove( it );  //Is that OK??
}

QMap<int, QString> mapCity;
mapCity.insert(1,"one");
mapCity.insert(2,"two");
...
mapCity.insert(9,"nine");
...

//Now, I want delete 1,2,3.

QMap<int, QString>::Iterator it;
for( it = mapCity.begin();  it != mapCity.end();  ++it)
{
    if( it.key() < 4 )
          mapCity.remove( it );  //Is that OK??
}

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[aamer4yu]

Remove takes key as argument, so I guess it should be map.remove(it.key());

[jedychen]

I want ask: use remove() in for(){},maybe wrong, this function will change the iterator's order. So I maybe cannot trival all items!

[caduel]

Assuming you use Qt4, try QMutableMapIterator instead.
(With the 'classic' STL style iterator you will get dangling iterators if you remove the item an iterator points to. Java style iterators are easier to use (correctly) imo.)

HTH

[jedychen]

unfortunately, I use Qt 3.3.8.I cannot find any functions to get dangling iterators.-_-

[caduel]

QMap<int, QString>::Iterator it;
for( it = mapCity.begin(); it != mapCity.end(); ) // remove increment here
{
  if( it.key() < 4 )
     mapCity.remove( it++ ); // this is ok; note POSTFIX operator here
  else
     ++it;
}

QMap<int, QString>::Iterator it;
for( it = mapCity.begin(); it != mapCity.end(); ) // remove increment here
{
  if( it.key() < 4 )
     mapCity.remove( it++ ); // this is ok; note POSTFIX operator here
  else
     ++it;
}

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