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
creationalSingletonView pattern
behavioralTemplate MethodView pattern
Basics
Categorybehavioralcreationalbehavioral
Summary———
IntentDefine 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.Define the skeleton of an algorithm in a base class and let subclasses override selected steps without changing the overall structure.
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 system needs exactly one shared instance of a class, and that instance must be globally accessible without allowing uncontrolled duplication.Several classes share the same algorithm structure, but some steps need to vary between implementations.
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
  • Can make dependencies harder to test if the singleton is used everywhere
  • May introduce hidden global state that complicates debugging and concurrency
  • Relies on inheritance, which can be less flexible than composition in some designs
  • May create a deep class hierarchy if many variations are needed
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.Singleton is useful for centralized services like configuration, logging, caching, and shared application state.Template Method is useful when you have repeated workflows with a common sequence of steps, such as processing orders, generating reports, and importing data.