The real difference is not ownership (composition versus aggregation), but rather type-information. A Decorator is always passed its delegatee. A Proxy might create it himself, or he might have it injected. But a Proxy always knows the (more) specific type of the delegatee. In other words, the Proxy and its delegatee will have the same … Read more
I was going to write up my own explanation but this Wikipedia article pretty much sums it up. Here is the basic concept: Copy-on-write (sometimes referred to as “COW”) is an optimization strategy used in computer programming. The fundamental idea is that if multiple callers ask for resources which are initially indistinguishable, you can give … Read more
Proxy, Decorator, Adapter, and Bridge are all variations on “wrapping” a class. But their uses are different. Proxy could be used when you want to lazy-instantiate an object, or hide the fact that you’re calling a remote service, or control access to the object. Decorator is also called “Smart Proxy.” This is used when you … Read more