Analysis

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Evaluate design patterns side by side across intent, tradeoffs, languages, and integration fit.

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Abstract FactoryAdapterBridgeBuilderChain of ResponsibilityCommandCompositeDecoratorFacadeFactory MethodFlyweightInterpreterIteratorMediatorMementoObserverPrototypeProxySingletonStateStrategyTemplate MethodVisitor

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Analysis

Pattern comparison

Reviewing 3 patterns.

Criteria
behavioralObserverView pattern
structuralProxyView pattern
creationalSingletonView pattern
Basics
Categorybehavioralstructuralcreational
Summary———
IntentDefine a subscription mechanism so multiple observers can react to subject events without the subject knowing concrete subscriber details.Provide a surrogate or placeholder for another object to control access to it.Ensure a class has only one instance and provide a global access point to it.
Decision factors
ProblemA system needs to notify multiple dependent objects when state changes occur, but hardcoding those dependencies makes the design rigid and tightly coupled.A client needs to interact with an object indirectly because the real object may be expensive, sensitive, or remote.A system needs exactly one shared instance of a class, and that instance must be globally accessible without allowing uncontrolled duplication.
Tradeoffs
  • 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
  • Adds another layer of indirection
  • Can make the design more complex when the extra control is unnecessary
  • Can make dependencies harder to test if the singleton is used everywhere
  • May introduce hidden global state that complicates debugging and concurrency
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
  • Web
  • Backend
  • Event-driven systems
  • Web
  • Backend
  • Mobile
  • UI kits
  • Cross-platform systems
  • Web
  • Backend
  • Mobile
  • UI kits
  • Cross-platform systems
Integration notesObservers work well inside a single application boundary for UI events, domain events, and in-process notifications where subscribers change dynamically.Proxy is useful for lazy loading, access control, caching, logging, and remote service wrappers.Singleton is useful for centralized services like configuration, logging, caching, and shared application state.