Apr 3, 2026

Template Method Pattern Guide: How Do You Keep the Flow but Change Some Steps?

In real code, you often see processes where the overall flow stays mostly the same but a few steps vary by case. If you copy the whole flow every time, duplication grows. If you generalize everything too early, the structure becomes hard to read. The template method pattern is a classic way to handle this.

In this post, we will cover:

what the template method pattern is
when it fits well
why it helps separate shared flow from changing steps
how it differs from the strategy pattern

The key idea is that the template method pattern keeps the high-level algorithm in one place while letting subclasses vary specific steps.

What is the template method pattern?

The template method pattern places the overall sequence of work in a base class, while allowing subclasses to implement or override certain parts.

In simple terms:

keep the big flow shared
vary only selected steps

For example, if a process is:

validate input
transform data
save it
run post-processing

then the shared sequence can stay stable while only transformation or post-processing changes.

Why is it useful?

Without this pattern, similar flows often get copied across multiple classes.

That leads to:

duplicated shared logic
more places to modify when the common flow changes
weaker visibility into the overall structure

The template method pattern helps when the goal is “keep the flow in one place.”

When does it fit well?

when the execution order is mostly fixed
when only a few steps vary
when you want to strongly preserve the common procedure

So it works well for problems where the overall workflow is stable but step details differ.

How is it different from strategy?

Both deal with changing behavior, but they do so differently.

strategy pattern: swap behavior through interchangeable objects
template method: keep the main procedure in a base class and vary selected steps

So template method is more inheritance-oriented, while strategy is more composition-oriented.

Common misunderstandings

1. If code is shared, it must be template method

Not necessarily. The key point is not shared code alone, but a shared algorithm order.

2. Template method is inheritance, so it is always a bad idea

Inheritance can be overused, but for stable shared procedures it can still be natural.

3. It is always simpler than strategy

Not always. If variation points are many and more flexible composition is needed, strategy may fit better.

Simple Example

abstract class DataProcessor {
  process(): void {
    this.validate();
    this.transform();
    this.save();
  }

  protected validate(): void {
    console.log('validate input');
  }

  protected abstract transform(): void;

  protected save(): void {
    console.log('save result');
  }
}

class CsvProcessor extends DataProcessor {
  protected transform(): void {
    console.log('transform csv data');
  }
}

new CsvProcessor().process();

The full flow stays fixed in process(), while the subclass changes only the variable step transform().

FAQ

Q. Where should beginners look for this pattern?

It is a good fit when very similar process flows keep appearing in multiple classes.

Q. Is a hook method the same as template method?

Not exactly. Hook methods are often optional extension points inside a template method structure.

Q. How do I choose between template method and strategy?

Ask whether you want to share the procedure through inheritance or swap behavior through separate collaborating objects.

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