I'm making use of the decorator pattern for one of the first times, as part of a Uni project. As far as I can see, the pattern seems to be meant more for adding functionality in a modular manner, however we've been taught it with uses such as a coffee or pizza maker, where the object has modular components that are added - changing properties rather than behaviour.

I'm trying to make the most of both uses, however I've come up with a question. In the example in the book we're using (Head First Design Patterns), the pattern is used in a coffee shop creating different coffees. So, for example, milk, froth, sugar, sprinkles are all decorators.

How would you implement a system that used the same decorator multiple times (for example, a coffee with two sugars)? Would you rewrap the coffee, or give sugar a quantity property? Or (as i'm starting to suspect) would this never be an issue as the pattern isn't designed to be used this way?