You cannot create an iterator by yourself. Instead, you must ask a map to give you one. An iterator is as big as a pointer; on 32-bit machines that means 4 bytes, on 64-bit machines, 8 bytes. That makes copying iterators very fast. Iterators behave in a similar way to pointers, and they are almost as fast as pointers. See the TQMap example.
TQMap is highly optimized for performance and memory usage, but the trade-off is that you must be more careful. The only way to traverse a map is to use iterators. TQMap does not know about its iterators, and the iterators don't even know to which map they belong. That makes things fast but a bit dangerous because it is up to you to make sure that the iterators you are using are still valid. TQDictIterator will be able to give warnings, whereas TQMapIterator may end up in an undefined state.
For every Iterator there is also a ConstIterator. You must use the ConstIterator to access a TQMap in a const environment or if the reference or pointer to the map is itself const. Its semantics are the same, but it only returns const references to the item it points to.
Prefix ++ makes the succeeding item current and returns an iterator pointing to the new current item. The iterator cannot check whether it reached the end of the map. Incrementing the iterator returned by end() causes undefined results.
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
.PP
Postfix ++ makes the succeeding item current and returns an iterator pointing to the new current item. The iterator cannot check whether it reached the end of the map. Incrementing the iterator returned by end() causes undefined results.
Prefix -- makes the previous item current and returns an iterator pointing to the new current item. The iterator cannot check whether it reached the beginning of the map. Decrementing the iterator returned by begin() causes undefined results.
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
.PP
Postfix -- makes the previous item current and returns an iterator pointing to the new current item. The iterator cannot check whether it reached the beginning of the map. Decrementing the iterator returned by begin() causes undefined results.
