Template Method vs Alternatives: When to Use Each

The Template Method Pattern is often confused with Strategy Pattern because both deal with algorithm variation. Understanding when to use each requires analyzing whether the algorithm structure is stable and whether you need runtime flexibility.
Template Method
Algorithm structure fixed at compile time via inheritance. Subclasses customize specific steps.
vs
Strategy Pattern
Entire algorithm swappable at runtime via composition. Context delegates to strategy object.
Use Template Method When:
First, Algorithm Structure is Stable: If the sequence of steps rarely changes but individual step implementations vary, Template Method is appropriate. Example: All payment processors follow authorize, capture, and settle steps, but authorization mechanisms differ (credit card, PayPal, cryptocurrency).
Second, Subclasses Share Common Behavior: When multiple classes need to inherit shared concrete methods along with customizable steps. Template Method leverages inheritance to reduce duplication. Example: All report generators format headers and footers identically but have different data rendering logic.
Third, You Want to Enforce Algorithm Invariants: When the base class must control the algorithm flow to ensure certain steps always execute in a specific order. Making the template method final prevents subclasses from violating these constraints.
Template Method is Overkill When: You only have one or two subclasses, the algorithm structure changes frequently, or you need to switch algorithms at runtime. In these cases, Strategy Pattern (composition) is more flexible than Template Method (inheritance).
Use Strategy Pattern When:
First, Runtime Algorithm Selection: If you need to switch algorithms dynamically based on user input or system state, Strategy Pattern is superior. Example: A navigation app switches between fastest route, shortest route, and scenic route strategies based on user preference.
Second, Algorithm is Completely Different: When subclasses don't share any common steps and would leave many hook methods empty. Strategy avoids bloated base classes with unused methods.
Third, Avoiding Inheritance Limitations: Strategy Pattern uses composition, allowing you to combine multiple strategies or switch strategies without subclassing. Template Method locks you into a single inheritance hierarchy.
Interview Tip: A common question is "Why not just use Strategy everywhere?" Answer: Template Method provides better code reuse for stable algorithm structures and enforces invariants through inheritance, but Strategy offers more flexibility when algorithms need to change at runtime or are completely independent.
Hybrid Approach: You can combine both patterns. Use Template Method to define the overall workflow and Strategy Pattern for individual steps. Example: A data export system uses Template Method for extract, transform, load steps but uses Strategy Pattern to swap transformation algorithms (normalize, aggregate, filter) within the transform step.
Comparison with Factory Method: Factory Method is actually a specialized application of Template Method where the varying step is object creation. If your template method only differs in the type of objects it creates, you might be implementing Factory Method Pattern instead.

💡 Key Takeaways

✓Template Method uses inheritance with fixed structure; Strategy uses composition with swappable algorithms

✓Choose Template Method for stable workflows with varying steps; Strategy for runtime algorithm selection

✓Template Method enforces invariants via final methods; Strategy allows complete algorithm replacement

✓Template Method can be overkill for simple cases or frequently changing structures

✓Hybrid approach uses Template Method for workflow and Strategy for individual step customization

📌 Examples

1Payment processing: Template Method for authorize-capture-settle workflow

2Route planning: Strategy Pattern for swapping routing algorithms at runtime

3Data export: Template Method for ETL pipeline with Strategy for transformation step

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