Analysis

Compare patterns

Evaluate design patterns side by side across intent, tradeoffs, languages, and integration fit.

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Analysis

Pattern comparison

Reviewing 3 patterns.

Criteria
behavioralCommandView pattern
behavioralIteratorView pattern
creationalSingletonView pattern
Basics
Categorybehavioralbehavioralcreational
SummaryEncapsulate a request as an object so it can be invoked, queued, logged, or undone independently of the receiver that performs the work.——
IntentEncapsulate a request as an object so it can be invoked, queued, logged, or undone independently of the receiver that performs the work.Provide 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.
Decision factors
ProblemA system needs to trigger actions without tightly coupling the code that requests an operation to the code that performs it, and it may also need queuing, history, or undo support.A 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.
Tradeoffs
  • Introduces extra classes or objects for each action.
  • Can feel heavier than direct method calls when the workflow is simple.
  • Makes requests more flexible, loggable, and replayable.
  • 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
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
  • frontend
  • backend
  • integration
  • Web
  • Backend
  • Mobile
  • UI kits
  • Cross-platform systems
  • Web
  • Backend
  • Mobile
  • UI kits
  • Cross-platform systems
Integration notesCommands work well for UI actions, background jobs, workflow steps, and undoable operations because invokers can trigger commands without depending on receiver details.Iterator 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.