Analysis

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Analysis

Pattern comparison

Reviewing 3 patterns.

Criteria
structuralFlyweightView pattern
behavioralIteratorView pattern
structuralProxyView pattern
Basics
Categorystructuralbehavioralstructural
Summary———
IntentUse sharing to support large numbers of fine-grained objects efficiently by separating shared intrinsic state from per-object extrinsic state.Provide a way to access elements of an aggregate sequentially while hiding the underlying representation.Provide a surrogate or placeholder for another object to control access to it.
Decision factors
ProblemA system creates a large number of similar objects, but storing all of their state separately uses too much memory.A collection needs to be traversed without exposing how it is stored internally.A client needs to interact with an object indirectly because the real object may be expensive, sensitive, or remote.
Tradeoffs
  • 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
  • Can add extra classes and abstraction for simple collections
  • May be unnecessary when built-in language iteration is already enough
  • Adds another layer of indirection
  • Can make the design more complex when the extra control is unnecessary
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 notesFlyweight is useful when thousands or millions of similar objects need to be represented efficiently, such as trees, glyphs, tiles, or UI tokens.Iterator is useful for pagination, custom collections, ordered traversal, and any case where clients should not know the internal data structure.Proxy is useful for lazy loading, access control, caching, logging, and remote service wrappers.