Analysis

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Analysis

Pattern comparison

Reviewing 3 patterns.

Criteria
creationalFactory MethodView pattern
behavioralObserverView pattern
creationalSingletonView pattern
Basics
Categorycreationalbehavioralcreational
Summary———
IntentDefine a creation method behind a common interface so specialized creators can decide which concrete product to instantiate without changing the surrounding workflow.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 workflow needs to create one of several related concrete objects, but constructing them directly in client code spreads creation logic and tightly couples the caller to specific implementations.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
  • Adds extra indirection and more types compared with direct construction
  • Can feel unnecessarily abstract when object creation is simple and unlikely to vary
  • 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
  • Applications
  • APIs
  • Frameworks
  • Service layers
  • Web
  • Backend
  • Event-driven systems
  • Web
  • Backend
  • Mobile
  • UI kits
  • Cross-platform systems
Integration notesFactory Method is useful when framework hooks, integrations, or environment-specific workflows need to create interchangeable implementations behind a stable contract.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.