Equivalent of UIScrollViewDelegate in Cocoa?

I am implementing a custom NSScroller class and I need to know when the scrollview is about to scro开发者_StackOverflow社区ll and when it finished doing so. What would be an equivalent of UIScrollViewDelegate's viewDidScroll, etc for NSScrollView/NSScroller?

Subclass NSScrollView and override reflectScrolledClipView:. Don't forget to call super's implementation!