Analysis

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Analysis

Pattern comparison

Reviewing 3 patterns.

Criteria
structuralFacadeView pattern
behavioralIteratorView pattern
behavioralObserverView pattern
Basics
Categorystructuralbehavioralbehavioral
SummaryProvide a simplified high-level interface that coordinates a complex subsystem behind a smaller and easier-to-use API.——
IntentProvide a simplified high-level interface that coordinates a complex subsystem behind a smaller and easier-to-use API.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 client needs to perform a recurring workflow that spans several subsystem classes, but direct coordination makes the code noisy and tightly coupled.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
  • Can become a dumping ground if boundaries are unclear.
  • May obscure useful lower-level capabilities from advanced consumers.
  • Simplifies the most common entry points for the system.
  • 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
  • applications
  • apis
  • service layers
  • Web
  • Backend
  • Mobile
  • UI kits
  • Cross-platform systems
  • Web
  • Backend
  • Event-driven systems
Integration notesFacades are useful when exposing a stable boundary over a multi-service or mixed-language backend, or when presenting a consistent UI entry point over multiple readiness checks.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.