🔍 Decorator vs Proxy

✅ Purpose of Comparison

Both Decorator and Proxy follow a similar structural pattern—wrapping another object with the same interface. However, they differ fundamentally in their intent and application. This comparison clarifies how and when to use each.

✅ Comparison Overview

Aspect	Decorator	Proxy
Purpose	Add responsibilities or features	Control access or add indirection
Primary Use Case	Enhance behavior (e.g., logging, caching)	Control access (e.g., lazy loading, auth)
Object Creation	Can be stacked in layers	Usually 1-to-1 with the real subject
Transparency	May introduce side effects	Often aims to be transparent to the caller
Structural Form	Chain of wrappers	Surrogate for one specific object

✅ Similarities

• Both implement the same interface as the wrapped object.
• Both wrap another class internally.
• Both are used to extend functionality without modifying the original.

✅ Key Differences

Aspect	Decorator	Proxy
Design Intent	Add new responsibilities dynamically	Restrict or manage access
Runtime Flexibility	Multiple decorators can be layered	Typically used as a static wrapper
Client Awareness	May know it’s using a decorator	Usually unaware it’s using a proxy

✅ When to Choose Which

• ✅ Want to dynamically add behavior at runtime → use Decorator
• ✅ Need to enforce access control, logging, or lazy loading → use Proxy
• ✅ Expect multiple behavior combinations → Decorator is more appropriate
• ✅ Just want a single layer to intercept or guard access → Proxy is simpler

✅ UML Class Diagram

Decorator Pattern

Proxy Pattern

✅ Practical Tips for Implementation

• ✅ Decorator is ideal when you want to chain multiple features (e.g., logging + validation).
• ✅ Proxy is best when you need a guard layer like authentication, permission checks, or caching.
• ▶️ In real-world design, they may even coexist—for example, a Proxy that wraps a Decorator, or vice versa.

✅ Summary

• Decorator focuses on behavioral enhancement, often used in layers.
• Proxy focuses on access control or interface indirection.
• While structurally similar, they serve distinct design intents.
• Clear identification of your purpose—behavior extension vs access management—is key to selecting the right pattern.