There are two general techniques for NSView subclasses to handle clicks and drags. MouseTrackingInACell is separate and more complex (although some techniques transfer).

Modal style: your function does not return until the mouse goes up.

• (void)mouseDown:(NSEvent *)firstEvent { // Handle the initial mouse down. NSEvent *latestEvent; while((latestEvent = self window] nextEventMatchingMask:[[NSLeftMouseDraggedMask | NSLeftMouseUpMask untilDate:[NSDate distantFuture] inMode:NSEventTrackingRunLoopMode dequeue:YES]) && [latestEvent type] != NSLeftMouseUp) { // Handle the mouse drag. } self window] discardEventsMatchingMask:[[NSAnyEventMask beforeEvent:latestEvent]; // Handle the mouse up. }

*Advantages

*You don’t need to use ivars because everything happens in one function. *You write the code that gets the events yourself, so you can do whatever you want. *It’s modal, so you don’t have to worry about anything else happening.

*Notes

*You have to specify the RunLoop mode to use. You probably want NSEventTrackingRunLoopMode. *Send -discardEventsMatchingMask:beforeEvent: afterward to make sure other events that happen during the drag are ignored. *Remember that there’s a difference between, for example, NSLeftMouseUp and NSLeftMouseUpMask. If necessary, you can use NSEventMaskFromType().

Non-modal style: you let the system tell you when a drag event occurs.

• (void)mouseDown:(NSEvent *)anEvent { self window] disableCursorRects]; // Handle the mouse down. }
• (void)mouseDragged:([[NSEvent *)anEvent { // Handle the mouse drag. If the mouse is not dragged, this method is not invoked. }
• (void)mouseUp:(NSEvent *)anEvent { // Handle the mouse up. [[self window] enableCursorRects]; }

*Advantages

*It’s arguably simpler. *Subclassers can override just one of the methods to change a portion of the behavior.

*Notes

• -disableCursorRects is necessary if you want to have a custom cursor persist during the drag.