johnnystefan/pattern-composite

Skill: Implement Composite Pattern

Purpose

Composes objects into tree structures to represent part-whole hierarchies. It lets clients treat individual objects and compositions of objects uniformly.

Procedural Instructions

1. Identify Tree Structure: Ensure your model can be represented as a tree (e.g., File system, UI components).
2. Define Component Interface: Declare common operations for both simple and complex elements.
3. Implement Leaf: Create classes for basic elements that have no children.
4. Implement Composite: Create container classes that store child components and delegate work to them.

TypeScript Example

interface Component {
  execute(): string;
}

class Leaf implements Component {
  execute() {
    return 'Leaf';
  }
}

class Composite implements Component {
  private children: Component[] = [];

  add(c: Component) {
    this.children.push(c);
  }

  execute(): string {
    const results = this.children.map((child) => child.execute());
    return `Branch(${results.join('+')})`;
  }
}

Payoff

• Polymorphism: Clients work with complex structures as if they were single objects.
• Flexibility: Easy to add new element types to the tree.