🔍 Command vs Template Method

✅ Purpose of Comparison

Both Command and Template Method are powerful design patterns for structuring processing logic and increasing modularity.
While they may appear similar in enabling step-level customization, they are fundamentally different in control flow, flexibility, and intent.

This comparison highlights key distinctions and use cases to help determine which pattern best suits a given design problem.

✅ Comparison Overview

Item	Command	Template Method
Implementation	Interface + object injection	Abstract class inheritance
Flexibility	High (commands can be changed at runtime)	Moderate (execution flow is fixed)
Testability	High (individual commands are testable)	Moderate (requires testing via subclass)
Primary Use Case	Delayed execution, action logging, macro operations	Fixed process flow with overridable steps
Extensibility	High (add more commands as needed)	Moderate (limited customization points)
Usage Style	Encapsulate each behavior as an object	Define a fixed algorithm structure

✅ Similarities

• Both aim to modularize behavior and isolate points of variation.
• Both use interface abstraction or method overriding to delegate specific logic.
• Both improve reusability and clarity of processing steps compared to inline logic.

✅ Key Differences

Aspect	Command	Template Method
Control Flow	Client controls execution by passing commands	Superclass dictates the flow
Reusability Granularity	Fine-grained (individual commands)	Coarse-grained (entire flow)
State Handling	Commands can hold and track internal state	Mostly stateless, focused on step-level customization
Execution Timing	Supports deferred or asynchronous execution	Executed immediately when called

✅ When to Choose Which

• ✅ Need for action recording, queuing, or delayed invocation → Command
• ✅ Have a fixed process with interchangeable steps → Template Method
• ✅ Want to log or undo operations → Command
• ✅ Need standardized flow with minor variations → Template Method

✅ UML Class Diagram

Command Pattern

Template Method Pattern

✅ Practical Tips for Implementation

• ✅ Command is ideal for features like Undo/Redo, macros, and action logging, particularly in GUI or CLI tools.
• ✅ Template Method shines in structured tasks like report generation, data export, and file processing, where the flow is mostly static.
• ▶️ In scenarios where you need both a fixed sequence and dynamic behavior injection, a synergistic approach may be valuable—e.g., using Command objects within a Template Method flow.

✅ Summary

• Command encapsulates behavior as standalone objects, providing maximum flexibility and control over execution timing and composition.
• Template Method enforces a consistent processing structure while allowing fine-grained customization via method overrides.
• Choosing the right pattern depends on the required level of runtime flexibility, processing granularity, and design control.