6.Design Patterns

Reusable design structures and the trade-offs behind creational, structural, and behavioral patterns.

A single shared instance, initialization safety, lifecycle, testability, and global-state trade-offs.

Interposing an object to control or augment access to another object while preserving its contract.

Fixing an algorithm skeleton while allowing selected steps to vary in subclasses or callbacks.

Separating object creation decisions from clients that consume the created abstraction.

Representing state-dependent behavior with explicit state objects instead of sprawling conditionals.

Constructing complex objects step by step with readable optional configuration and validation.

Encapsulating interchangeable algorithms or policies behind a common contract.

Notifying registered observers about subject changes and managing coupling, ordering, and lifecycle.

Adding composable behavior around an object without changing the wrapped implementation.

Passing a request through an ordered pipeline of handlers that may process, enrich, reject, or forward it.

Translating one interface/protocol/data model into the contract expected by a client.