Analysis

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Abstract FactoryAdapterBridgeBuilderChain of ResponsibilityCommandCompositeDecoratorFacadeFactory MethodFlyweightInterpreterIteratorMediatorMementoObserverPrototypeProxySingletonStateStrategyTemplate MethodVisitor

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Analysis

Pattern comparison

Reviewing 3 patterns.

Criteria
structuralFlyweightView pattern
behavioralIteratorView pattern
behavioralObserverView pattern
Basics
Categorystructuralbehavioralbehavioral
Summary———
IntentUse sharing to support large numbers of fine-grained objects efficiently by separating shared intrinsic state from per-object extrinsic state.Provide 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.
Decision factors
ProblemA system creates a large number of similar objects, but storing all of their state separately uses too much memory.A 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.
Tradeoffs
  • Adds complexity because state must be split into shared and unshared parts
  • Can be harder to understand when many objects depend on an external context
  • 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
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
  • Mobile
  • UI kits
  • Cross-platform systems
  • Web
  • Backend
  • Event-driven systems
Integration notesFlyweight is useful when thousands or millions of similar objects need to be represented efficiently, such as trees, glyphs, tiles, or UI tokens.Iterator 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.