TemplateMethod

Template Method Pattern

Intent

Define the skeleton of an algorithm in an operation, deferring some steps to subclasses. Template Method lets subclasses redefine certain steps of an algorithm without changing the algorithm's structure.

Problem

You have multiple classes with similar algorithms that differ only in some steps. Code duplication occurs when you implement the algorithm in each class.

Solution

The Template Method pattern breaks down an algorithm into steps and allows subclasses to override specific steps while keeping the overall structure intact.

When to Use

• You want to let clients extend only particular steps of an algorithm, but not the whole algorithm or its structure
• You have several classes with almost identical algorithms with minor differences
• You want to control the extension points for subclasses

C# Implementation

See the Program.cs file for data exporters (CSV and JSON) sharing a common workflow template.

Pros

• Can let clients override only certain parts of a large algorithm
• Can pull duplicate code into a superclass
• Promotes code reuse

Cons

• Clients may be limited by the provided skeleton
• Might violate Liskov Substitution Principle by suppressing default step via subclass
• Template methods tend to be harder to maintain as they grow