Analysis

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Abstract FactoryAdapterBridgeBuilderChain of ResponsibilityCommandCompositeDecoratorFacadeFactory MethodFlyweightInterpreterIteratorMediatorMementoObserverPrototypeProxySingletonStateStrategyTemplate MethodVisitor

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Analysis

Pattern comparison

Reviewing 3 patterns.

Criteria
structuralCompositeView pattern
structuralFlyweightView pattern
behavioralObserverView pattern
Basics
Categorystructuralstructuralbehavioral
SummaryCompose objects into tree structures to represent part-whole hierarchies and let clients work with individual and composite objects through the same interface.——
IntentCompose objects into tree structures to represent part-whole hierarchies and let clients work with individual and composite objects through the same interface.Use sharing to support large numbers of fine-grained objects efficiently by separating shared intrinsic state from per-object extrinsic state.Define a subscription mechanism so multiple observers can react to subject events without the subject knowing concrete subscriber details.
Decision factors
ProblemA system needs to treat individual objects and groups of objects uniformly, but the hierarchy becomes difficult to manage with separate code paths.A system creates a large number of similar objects, but storing all of their state separately uses too much memory.A system needs to notify multiple dependent objects when state changes occur, but hardcoding those dependencies makes the design rigid and tightly coupled.
Tradeoffs
  • Can make the design more abstract and harder to follow.
  • May require careful handling of operations that only apply to some nodes in the tree.
  • Makes recursive tree operations and client code much simpler.
  • 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
  • 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 notesComposite is useful when a hierarchy of nested objects should expose a common interface, such as files and folders, menus and submenus, org charts, widget trees, or scene graphs.Flyweight is useful when thousands or millions of similar objects need to be represented efficiently, such as trees, glyphs, tiles, or UI tokens.Observers work well inside a single application boundary for UI events, domain events, and in-process notifications where subscribers change dynamically.