For a well-documented feature,
accessoryView feature takes a little bit of fiddling to implement.
NSAlert is behind the standard pop-up modal alert window that’s familiar to everyone, often popping into the foreground and grabbing your attention, refusing to go away until you acknowledge its existence:
NSAlert boxes can, by default, display any number of buttons (c.f. the classic “Save/Delete/Cancel” triumvirate), but advanced features require a little more jiggery-pokery. This mainly comes in the form of its
accessoryView property, which allows you to add an
NSView to the alert proper. At first you might be tempted to programatically create an
NSView, adding the required elements in
init methods and the like, but it turns out it’s actually a bit easier to use
nib files to hold all of that. This is how to do so.