johnnystefan/pattern-iterator

Skill: Implement Iterator Pattern

Purpose

Provides a way to access the elements of an aggregate object sequentially without exposing its underlying representation (list, stack, tree, etc.).

Procedural Instructions

1. Declare Iterator Interface: Define methods for fetching the next() element and checking if there are hasMore() items.
2. Declare Collection Interface: Define a method to createIterator().
3. Implement Concrete Iterator: Encapsulate traversal logic and maintain the current position for a specific collection type.
4. Implement Concrete Collection: Return a new instance of the appropriate iterator.

TypeScript Example

interface MyIterator<T> {
  next(): T;
  hasNext(): boolean;
}

class AlphabeticalIterator implements MyIterator<string> {
  private position: number = 0;
  constructor(private collection: string[]) {}
  next(): string {
    return this.collection[this.position++];
  }
  hasNext(): boolean {
    return this.position < this.collection.length;
  }
}

interface IterableCollection {
  getIterator(): MyIterator<string>;
}

Payoff

• Uniformity: Client code can work with various collections using a single iterator interface.
• Clean Code: Moves bulky traversal algorithms out of business logic.