QMap to keep the model statistcs

[gyre]

You would.

Yes, of course. For instance like so:

QHash<int, int> m_lookupIndex; // maps id to index in the list
struct Item{
  int id;
  int count;
  Item(){id=-1;count=0;}
};
QList<Item> m_data;
 
void Model::insert(...){
  int id = getId();
  Item item;
  item.id = id;
  item.count = 1;
  int index = m_data.count();
  m_list.append(item);
  m_lookupIndex[id] = index;
  //...
}
 
QModelIndex Model::idToIndex(int id){
  if(!m_lookupIndex.contains(id))
    return QModelIndex();
  int ind = m_lookupIndex[id];
  // it'd be 2 times faster using iterators, but it's just an example, so...
  return index(ind, 0);
}

QHash<int, int> m_lookupIndex; // maps id to index in the list
struct Item{
  int id;
  int count;
  Item(){id=-1;count=0;}
};
QList<Item> m_data;

void Model::insert(...){
  int id = getId();
  Item item;
  item.id = id;
  item.count = 1;
  int index = m_data.count();
  m_list.append(item);
  m_lookupIndex[id] = index;
  //...
}

QModelIndex Model::idToIndex(int id){
  if(!m_lookupIndex.contains(id))
    return QModelIndex();
  int ind = m_lookupIndex[id];
  // it'd be 2 times faster using iterators, but it's just an example, so...
  return index(ind, 0);
}

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fuh you got me confused I must say ...thanks anyway