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
structuralAdapterView pattern
behavioralObserverView pattern
behavioralStateView pattern
Basics
Categorystructuralbehavioralbehavioral
SummaryConvert the interface of a class or module into another interface clients expect.——
IntentAllow incompatible interfaces to work together without changing the consuming code.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 talk to a legacy class or external service whose interface does not match the rest of the codebase.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
  • Adds an extra layer of indirection.
  • Can hide useful vendor-specific capabilities if overused.
  • Keeps integration code isolated from core domain logic.
  • 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
  • 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
  • Web
  • Backend
  • Event-driven systems
  • Web
  • Backend
  • Mobile
  • UI kits
  • Cross-platform systems
Integration notesAdapters are useful when exposing a stable boundary over a legacy API, vendor SDK, or payload format mismatch.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.