Proxy

Provide a surrogate or placeholder for another object to control access to it.

• Proxy
  • maintains a reference that lets the proxy access the real subject.
  • provides an interface identical to Subject's so that a proxy can be substituded for the real subject.
  • controls access to the real subject and may be responsible for creating and deleting it.
• Subject
  • defines the common interface for RealSubject and Proxy so that a Proxy can be used anywhere a RealSubject is expected.
• realSubject
  • defines the real object that the proxy represents.

• A remote proxy can hide the fact that an object resides in a different address space.
• A virtual proxy can perform optimizations such as creating an object on demand.
• both protection proxies and smart references allow additional housekeeping tasks when an object is accessed.