This array convenience method takes a comma-separated list of objects ending with nil.
nil
myArray = [NSArray arrayWithObjects:aDate, aValue, aStrin
Null terminated variable argument lists, or va_lists, keep walking the list of arguments until they encounter a placeholder or sentinel, which is nil.
va_list
Since the method has no way of knowing how many arguments you are passing, it needs the sentinel (nil) to tell where the list ends.