Sets the priority under which split view subviews maintain their width or height.
- macOS 10.8+
The index of the subview
Sets the priority 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.
The default is NSLayoutPriorityDefaultLow. There is no reason to use the default, but you should use priorities less than NSLayoutPriorityDragThatCannotResizeWindow.