johnnystefan/pattern-template-method

Skill: Implement Template Method Pattern

Purpose

Defines the skeleton of an algorithm in a superclass but lets subclasses override specific steps of the algorithm without changing its structure.

Procedural Instructions

1. Identify Common Algorithm Structure: Look for classes with similar methods that follow the same sequence of steps.
2. Define Abstract Superclass: Create a "template method" containing the sequence of calls to various steps.
3. Declare Algorithm Steps: Define the individual steps as abstract methods (must override) or hooks (optional override).
4. Implement Subclasses: Override the required steps to customize behavior.

TypeScript Example

abstract class DataMiner {
  public mine() {
    // Template Method
    this.openFile();
    this.extractData();
    this.closeFile();
  }
  abstract openFile(): void;
  abstract extractData(): void;
  closeFile() {
    console.log('File closed.');
  } // Default impl
}

class PDFMiner extends DataMiner {
  openFile() {
    console.log('Opening PDF...');
  }
  extractData() {
    console.log('Extracting PDF content...');
  }
}

Payoff

• Deduplication: Pulls duplicate code from subclasses into a single superclass.
• Control: Subclasses can only override specific parts of a large algorithm, reducing risk.