Assuming what? I don’t really get your question, you don’t seem like a complete newbie when it comes to actionscript. But the question seems so simple. Is this some issue with flash that I don’t know of? I haven’t used flash in a year or two now, but OOP always stays the same so here goes: Yes, in your example the only way to change the var _property is by initiating a new instance of the object and pass the value(object) to the constructor. Because you made the scope of the variable _property private it can only be accessed in the scope of the object, not outside of it. That is why you need a setter method when you want to be able to change that value, since you don’t want to do that, declaring the variable _property private is enough. This is called encapsulation (public, private, etc) and is really the very basic of object orientated programming and as3. Try learning more about encapsulation, for example by reading this tutorial.