Returns the child of a given item at a given index.
- macOS 10.5+
The rule editor that sent the message.
The index of the requested child criterion. This value must be in the range from
0up to (but not including) the number of children, as reported by the delegate in
Editor(_: number Of Children For Criterion: with:)
The parent of the requested child, or
nilif the rule editor is requesting a root criterion.
The type of the row.
An object representing the requested child (or root) criterion. This object is used by the delegate to represent that position in the tree, and is passed as a parameter in subsequent calls to the delegate.
The delegate must implement this method.