Analysis

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Abstract FactoryAdapterBridgeBuilderChain of ResponsibilityCommandCompositeDecoratorFacadeFactory MethodFlyweightInterpreterIteratorMediatorMementoObserverPrototypeProxySingletonStateStrategyTemplate MethodVisitor

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Analysis

Pattern comparison

Reviewing 3 patterns.

Criteria
structuralAdapterView pattern
structuralFacadeView pattern
behavioralObserverView pattern
Basics
Categorystructuralstructuralbehavioral
SummaryConvert the interface of a class or module into another interface clients expect.Provide a simplified high-level interface that coordinates a complex subsystem behind a smaller and easier-to-use API.—
IntentAllow incompatible interfaces to work together without changing the consuming code.Provide a simplified high-level interface that coordinates a complex subsystem behind a smaller and easier-to-use API.Define a subscription mechanism so multiple observers can react to subject events without the subject knowing concrete subscriber details.
Decision factors
ProblemA client needs to talk to a legacy class or external service whose interface does not match the rest of the codebase.A client needs to perform a recurring workflow that spans several subsystem classes, but direct coordination makes the code noisy and tightly coupled.A system needs to notify multiple dependent objects when state changes occur, but hardcoding those dependencies makes the design rigid and tightly coupled.
Tradeoffs
  • Adds an extra layer of indirection.
  • Can hide useful vendor-specific capabilities if overused.
  • Keeps integration code isolated from core domain logic.
  • Can become a dumping ground if boundaries are unclear.
  • May obscure useful lower-level capabilities from advanced consumers.
  • Simplifies the most common entry points for the system.
  • Notification flows can become hard to trace when many observers react to the same event
  • Observers may receive updates they do not need unless subscriptions are carefully designed
Practical fit
Languages
  • typescript
  • java
  • python
  • go
  • csharp
  • dotnet
  • react
  • angular
  • react-native
  • typescript
  • java
  • python
  • angular
  • react
  • react-native
  • csharp
  • dotnet
  • typescript
  • java
  • python
  • angular
  • react
  • react-native
  • csharp
  • dotnet
Platforms
  • applications
  • apis
  • service layers
  • integrations
  • applications
  • apis
  • service layers
  • Web
  • Backend
  • Event-driven systems
Integration notesAdapters are useful when exposing a stable boundary over a legacy API, vendor SDK, or payload format mismatch.Facades are useful when exposing a stable boundary over a multi-service or mixed-language backend, or when presenting a consistent UI entry point over multiple readiness checks.Observers work well inside a single application boundary for UI events, domain events, and in-process notifications where subscribers change dynamically.