methodopen

Methodopen is a term used in software development to describe a design approach that emphasizes exposing a well-defined public surface of methods for external use while keeping the internal state and implementation details private. The idea is to allow external code to extend or customize behavior by calling these methods rather than altering internal logic directly.

The term is not widely standardized and does not refer to a single formal specification. It appears in discussions about API design, plugin architectures, and the open-closed principle, where software is open to extension but closed to modification.

Key characteristics include a stable public method surface, clear contracts, versioning and deprecation policies, and explicit extension points such as hooks, adapters, or plugin interfaces. Access control and documentation are important to prevent misuse and preserve encapsulation.

Applications include libraries and frameworks that offer plugins or user extensions, services with customizable workflows, or GUI toolkits that allow plugins to register callbacks. A typical pattern involves defining a small set of public methods that callers can invoke and providing internal mechanisms for customizing behavior through configuration or extension modules. In a hypothetical text editor, methods like registerCommand or applyTheme could be public extension points.

Criticisms include risk of API bloat, increased maintenance burden, and performance overhead from indirection. Advocates argue it supports modularity and interoperability if the surface is carefully managed. See also Open-Closed Principle; API design; Plugin architecture; Software modularity.