Analysis

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Analysis

Pattern comparison

Reviewing 3 patterns.

Criteria
structuralCompositeView pattern
behavioralIteratorView pattern
behavioralStateView pattern
Basics
Categorystructuralbehavioralbehavioral
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.Provide a way to access elements of an aggregate sequentially while hiding the underlying representation.Allow an object to alter its behavior when its internal state changes by delegating state-specific behavior to separate state objects.
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 collection needs to be traversed without exposing how it is stored internally.An object behaves differently depending on its internal state, and conditional logic is becoming hard to manage.
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.
  • Can add extra classes and abstraction for simple collections
  • May be unnecessary when built-in language iteration is already enough
  • Can introduce many small classes if the state graph is large
  • State transitions may become harder to trace if spread across multiple classes
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
  • Mobile
  • UI kits
  • Cross-platform 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.Iterator is useful for pagination, custom collections, ordered traversal, and any case where clients should not know the internal data structure.State is useful for workflows, media players, order lifecycles, and any domain where behavior changes as the object moves through a lifecycle.