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Move

procedure Move(CurIndex, NewIndex: Integer);

Example​

procedure MoveFirstToLast(const Items: TStringList);
begin
  if (not Items.Sorted) and (Items.Count > 1) then
    Items.Move(0, Items.Count - 1);
end;

Usage​

Move relocates one string/object pair by detaching it, deleting the old entry and inserting at a new index.

  • Never call on a sorted TStringList; sorting already determines position.
  • Validate both indexes against the pre-move count and consider how deletion changes allowable insertion positions.
  • Do not treat the call as transactional; preserve recovery data before high-risk moves.

Additional Technical Info​

Move is declared by hidden ancestor TStrings and is normally used through a concrete visible descendant such as TStringList. The installed base algorithm is multi-step and is not rollback-safe.

Source-backed behaviour​

When indexes differ, the method batches updates, reads the pair, writes nil into the old object slot, deletes the old entry, then calls InsertObject at NewIndex. Detaching the object before deletion prevents an owning descendant from freeing it during the move.

This order creates a significant quirk for TStringList: if Sorted=True, deletion succeeds but InsertObject then raises EStringListError, so the entry has already been removed and its object detached. Invalid NewIndex, allocation or event failures can likewise leave the list missing the pair. Equal indexes do nothing.

Exchange swaps two existing pairs without delete/insert in TStringList. Delete and InsertObject are the destructive steps.

Official RTL references​

Created 2026-07-15