johnnystefan/pattern-singleton

Skill: Implement Singleton Pattern

Purpose

Ensures that a class has only one instance while providing a global access point to that instance. Crucial for shared resources like database connections.

Procedural Instructions

1. Private Constructor: Prevent direct instantiation with new.
2. Static Field: Store the unique instance.
3. Static Getter: Provide a method that initializes the instance (lazy loading) if it doesn't exist and returns it.

TypeScript Example

class Database {
  private static instance: Database;

  private constructor() {
    // Init logic (e.g., connect to DB)
  }

  public static getInstance(): Database {
    if (!Database.instance) {
      Database.instance = new Database();
    }
    return Database.instance;
  }

  public query(sql: string) {
    /* ... */
  }
}

Payoff

• Controlled Access: Strict control over a global resource.
• Memory Savings: Avoids creating multiple heavy objects for the same task.