Returns the priority of the subview’s width or height when resizing.
- macOS 10.8+
The index of the subview.
Returns the layout priority of the subview at the index.
The priority is the manner under which split view subviews hold their widths (for a vertical split view) or height (for a horizontal split view). The view with the lowest priority will be the first to take on additional width if the split view grows or shrinks.