DESIGN PATTERN
| Type : | St (Structural) |
| Intent : | Provide a surrogate or placeholder for another object to control access to it. |
| Applicability : | Proxy is applicable whenever there is a need for a more versatile or sophisticated reference to an object than a simple pointer. Here are several common situations in which the Proxy pattern is applicable : 1. A "remote proxy" provides a local representative for an object in a different address space. Coplien calls this kind of proxy an "Ambassador". 2. A "virtual proxy" creates expensive objects on demand. 3. A "protection proxy" controls access to the original object. Protection proxies are useful when objects should have different access rights. 4. A "smart reference" is a replacement for a bare pointer that performs additional actions when an object is accessed. Typical uses include - counting the number of references to the real object so that it can be freed automatically when there are no more references (also called smart pointers). - loading a persistent object into memory when it's first referenced. - checking that the real object is locked before it's accessed to ensure that no other object can change it. |