Analysis

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Analysis

Pattern comparison

Reviewing 3 patterns.

Criteria
structuralAdapterView pattern
behavioralMementoView pattern
behavioralObserverView pattern
Basics
Categorystructuralbehavioralbehavioral
SummaryConvert the interface of a class or module into another interface clients expect.——
IntentAllow incompatible interfaces to work together without changing the consuming code.Capture and externalize an object's state so it can be restored to a previous point in time.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 talk to a legacy class or external service whose interface does not match the rest of the codebase.An object's internal state must be saved and restored later without exposing its implementation details.A system needs to notify multiple dependent objects when state changes occur, but hardcoding those dependencies makes the design rigid and tightly coupled.
Tradeoffs
  • Adds an extra layer of indirection.
  • Can hide useful vendor-specific capabilities if overused.
  • Keeps integration code isolated from core domain logic.
  • Snapshots can consume memory if many states are stored.
  • Care must be taken to keep mementos immutable and hidden from outside code.
  • 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
  • go
  • csharp
  • dotnet
  • react
  • angular
  • react-native
  • typescript
  • java
  • python
  • angular
  • react
  • react-native
  • csharp
  • dotnet
  • typescript
  • java
  • python
  • angular
  • react
  • react-native
  • csharp
  • dotnet
Platforms
  • applications
  • apis
  • service layers
  • integrations
  • Web
  • Backend
  • Mobile
  • UI kits
  • Cross-platform systems
  • Web
  • Backend
  • Event-driven systems
Integration notesAdapters are useful when exposing a stable boundary over a legacy API, vendor SDK, or payload format mismatch.Memento is useful for undo/redo, checkpoints, draft recovery, and any workflow where state history matters.Observers work well inside a single application boundary for UI events, domain events, and in-process notifications where subscribers change dynamically.