Analysis

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Abstract FactoryAdapterBridgeBuilderChain of ResponsibilityCommandCompositeDecoratorFacadeFactory MethodFlyweightInterpreterIteratorMediatorMementoObserverPrototypeProxySingletonStateStrategyTemplate MethodVisitor

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Analysis

Pattern comparison

Reviewing 3 patterns.

Criteria
structuralFacadeView pattern
behavioralObserverView pattern
behavioralStateView pattern
Basics
Categorystructuralbehavioralbehavioral
SummaryProvide a simplified high-level interface that coordinates a complex subsystem behind a smaller and easier-to-use API.——
IntentProvide 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.Allow an object to alter its behavior when its internal state changes by delegating state-specific behavior to separate state objects.
Decision factors
ProblemA 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.An object behaves differently depending on its internal state, and conditional logic is becoming hard to manage.
Tradeoffs
  • 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
  • Can introduce many small classes if the state graph is large
  • State transitions may become harder to trace if spread across multiple classes
Practical fit
Languages
  • typescript
  • java
  • python
  • angular
  • react
  • react-native
  • csharp
  • dotnet
  • typescript
  • java
  • python
  • angular
  • react
  • react-native
  • csharp
  • dotnet
  • typescript
  • java
  • python
  • angular
  • react
  • react-native
  • csharp
  • dotnet
Platforms
  • applications
  • apis
  • service layers
  • Web
  • Backend
  • Event-driven systems
  • Web
  • Backend
  • Mobile
  • UI kits
  • Cross-platform systems
Integration notesFacades 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.State is useful for workflows, media players, order lifecycles, and any domain where behavior changes as the object moves through a lifecycle.