You can mix Objective-C and Swift code in a project, so it would be easy to progressively port code one class at a time. Porting NSView subclasses first would

You can mix Objective-C and Swift code in a project, so it would be easy to progressively port code one class at a time. Porting NSView subclasses first would give you a win, because if you use Swift the classes can draw themselves at design time in Interface Builder. (Objective-C view subclasses just draw a white rectangle in IB.)