Analysis

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Analysis

Pattern comparison

Reviewing 3 patterns.

Criteria
behavioralMediatorView pattern
behavioralMementoView pattern
behavioralObserverView pattern
Basics
Categorybehavioralbehavioralbehavioral
Summary———
IntentDefine an object that encapsulates communication between a set of objects, keeping them from referring to each other directly.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
ProblemMultiple objects need to coordinate behavior, but direct references between them create tight coupling and complex dependencies.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
  • The mediator can become large and complex if it takes on too much coordination logic.
  • Centralizing behavior can make the mediator a single point of failure if it is poorly designed.
  • 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
  • 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
  • Event-driven systems
Integration notesMediator is useful for chat systems, form coordination, workflow orchestration, and any domain where many components must collaborate without knowing about each other.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.