# Chain of Responsibility Pattern

> A design pattern that passes a request along an ordered list of handlers until one of them handles it.

Record: `architecture:chain-of-responsibility-pattern`
Kind: pattern
Layer: [Design Patterns Core](https://banes-lab.com/records/layer/design-patterns-core.md)
Severity: recommended
Scope: behavior, request handling, pipeline
Canonical: https://banes-lab.com/ontology#architecture-chain-of-responsibility-pattern

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [State Pattern](https://banes-lab.com/records/architecture/state-pattern.md) and before [Iterator Pattern](https://banes-lab.com/records/architecture/iterator-pattern.md).

## Repair

- Refactored by: Extract Handler Chain
- Detected by: long if/else ladders handling heterogeneous requests
- Violated by: one handler with nested conditionals for every case
- Measured by: handler cyclomatic complexity
- Enforced by: [design review](https://banes-lab.com/records/architecture/design-review.md)

## Requires

- [Uniform Handler Interface](https://banes-lab.com/records/lexicon/uniform-handler-interface.md)

## Reinforces

- [Open/Closed Principle (OCP)](https://banes-lab.com/records/architecture/open-closed.md)
- [Single Responsibility Principle (SRP)](https://banes-lab.com/records/architecture/single-responsibility.md)

## Enables

- [Pluggable Handling](https://banes-lab.com/records/lexicon/pluggable-handling.md)
- [Ordered Fallthrough](https://banes-lab.com/records/lexicon/ordered-fallthrough.md)

## Conflicts with

- [Monolithic Handler](https://banes-lab.com/records/lexicon/monolithic-handler.md)

## In tension with

- [Traceability](https://banes-lab.com/records/architecture/traceability.md)

## Tensions

- [Chain of Responsibility Pattern / Traceability](https://banes-lab.com/records/tension/chain-of-responsibility-pattern-traceability.md)

## Severity

- [recommended](https://banes-lab.com/records/vocabulary/severity-recommended.md)

## Category

- [Behavioral Patterns](https://banes-lab.com/records/architecture-category/behavioral-patterns.md)

## Linked from

- [Core Modular Design](https://banes-lab.com/ontology/principles/architecture-category-core-modular-design.md)
- [SOLID / Object-Oriented Design](https://banes-lab.com/ontology/principles/architecture-category-solid-object-oriented-design.md)
- [Observability / Auditability / Traceability](https://banes-lab.com/ontology/principles/architecture-category-observability-auditability-traceability.md)
- [Behavioral Patterns](https://banes-lab.com/ontology/lexicon/lexicon-category-behavioral-patterns.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The resolutions](https://banes-lab.com/ontology/schema/the-resolutions.md)