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
behavioralIteratorView pattern
behavioralObserverView pattern
creationalSingletonView pattern
Basics
Categorybehavioralbehavioralcreational
Summary———
IntentProvide a way to access elements of an aggregate sequentially while hiding the underlying representation.Define a subscription mechanism so multiple observers can react to subject events without the subject knowing concrete subscriber details.Ensure a class has only one instance and provide a global access point to it.
Decision factors
ProblemA collection needs to be traversed without exposing how it is stored internally.A system needs to notify multiple dependent objects when state changes occur, but hardcoding those dependencies makes the design rigid and tightly coupled.A system needs exactly one shared instance of a class, and that instance must be globally accessible without allowing uncontrolled duplication.
Tradeoffs
  • Can add extra classes and abstraction for simple collections
  • May be unnecessary when built-in language iteration is already enough
  • 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 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
  • Mobile
  • UI kits
  • Cross-platform systems
  • Web
  • Backend
  • Event-driven systems
  • Web
  • Backend
  • Mobile
  • UI kits
  • Cross-platform systems
Integration notesIterator is useful for pagination, custom collections, ordered traversal, and any case where clients should not know the internal data structure.Observers work well inside a single application boundary for UI events, domain events, and in-process notifications where subscribers change dynamically.Singleton is useful for centralized services like configuration, logging, caching, and shared application state.