An effect to apply to the animation.

Takes a string constant specifying fade-in or fade-out effects for the target: NSViewAnimationFadeInEffect and NSViewAnimationFadeOutEffect. If the target is a view and the effect is to fade out, the view is hidden at the end. If the effect is to fade in an initially hidden view and the end frame is non-empty, the view is unhidden at the end. If the target is a window, the window is ordered in or out as appropriate to the effect. This property is optional.

Available in Mac OS X v10.4 and later.