ViewRef detach([num index = -1 ])

Use along with #insert to move a View within the current container.

If the index param is omitted, the last ViewRef is detached. TODO(i): refactor insert+remove into move

Source 

ViewRef detach([num index = -1]) {
  if (index == -1) index = this.length - 1;
  return _element.detachView(index).ref;
}