If you want to be safe for future language improvements then you can write:
class Person { var _age var _name func SetDefaults(name = "John Doe" , age = 0) { if (name) _name = name if (age) _age = age } }
please note that instead of SetDefaults you could have an init function (the constructor) so your code will be much more easier to read. There is a small bug in the init constructor (when called with a different number of arguments) so you should wait few days for the next upcoming release.