Use cases
The Decorator pattern shines when used for implementing cross-cutting concerns [Lott14, page 223], [j.mp/wikicrosscut]. Examples of cross-cutting concerns are:
- Data validation
- Transaction processing (A transaction in this case is similar to a database transaction, in the sense that either all steps should be completed successfully, or the transaction should fail.)
- Caching
- Logging
- Monitoring
- Debugging
- Business rules
- Compression
- Encryption
In general, all parts of an application that are generic and can be applied to many other parts of it, are considered cross-cutting concerns.
Another popular example of using the Decorator pattern is Graphical User Interface (GUI) toolkits. In a GUI toolkit, we want to be able to add features such as borders, shadows, colors, and scrolling to individual components/widgets [GOF95, page 196].
