Analysis

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Analysis

Pattern comparison

Reviewing 3 patterns.

Criteria
behavioralIteratorView pattern
behavioralObserverView pattern
behavioralStateView pattern
Basics
Categorybehavioralbehavioralbehavioral
Summary———
IntentProvide 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.Allow an object to alter its behavior when its internal state changes by delegating state-specific behavior to separate state objects.
Decision factors
ProblemA 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.An object behaves differently depending on its internal state, and conditional logic is becoming hard to manage.
Tradeoffs
  • 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
  • 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
  • Event-driven systems
  • Web
  • Backend
  • Mobile
  • UI kits
  • Cross-platform systems
Integration notesIterator 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.State is useful for workflows, media players, order lifecycles, and any domain where behavior changes as the object moves through a lifecycle.