function Extract: T; inline;
T __fastcall Extract();
Removes the item from the beginning of the queue.
An OnNotify event occurs indicating an item was removed from the queue.
Extract is the same as Dequeue except for the event code indicating an element was extracted rather than removed. Extract is a more generic method, common to all collections, whereas Dequeue is specialized for TQueue. You can use either of the two functions to obtain and remove the item at the beginning of the queue.
This is a O(1) operation.