Proxy

A proxy is a design pattern in which a wrapper object stands in for a real object, and is called by the client instead of that real object. Because the proxy implements the same interface as the object it stands in for, using it looks identical, from the client’s point of view, to using the real object directly.

A proxy can simply forward every call through to the real object unchanged, but its usefulness comes from what it can add along the way, such as caching a result when the real object is expensive to call, checking preconditions before letting a call through, deferring creation of the real object until it’s actually needed, or restricting access to it altogether. In every case, the client remains unaware that it isn’t talking to the real object.