Analysis

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Analysis

Pattern comparison

Reviewing 3 patterns.

Criteria
behavioralIteratorView pattern
creationalSingletonView pattern
behavioralVisitorView pattern
Basics
Categorybehavioralcreationalbehavioral
Summary———
IntentProvide a way to access elements of an aggregate sequentially while hiding the underlying representation.Ensure a class has only one instance and provide a global access point to it.Separate an algorithm from the object structure it operates on by moving behavior into visitor objects.
Decision factors
ProblemA collection needs to be traversed without exposing how it is stored internally.A system needs exactly one shared instance of a class, and that instance must be globally accessible without allowing uncontrolled duplication.You need to perform operations across a set of different object types without stuffing all the logic into the objects themselves.
Tradeoffs
  • Can add extra classes and abstraction for simple collections
  • May be unnecessary when built-in language iteration is already enough
  • Can make dependencies harder to test if the singleton is used everywhere
  • May introduce hidden global state that complicates debugging and concurrency
  • Requires updating the visitor interface when new element types are added
  • Can be awkward if the object structure changes often
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 notesIterator is useful for pagination, custom collections, ordered traversal, and any case where clients should not know the internal data structure.Singleton is useful for centralized services like configuration, logging, caching, and shared application state.Visitor is useful for AST processing, reporting, cart calculations, and exporting object structures to alternate formats.