johnnystefan/pattern-mediator

Skill: Implement Mediator Pattern

Purpose

Reduces chaotic dependencies between objects by forcing them to collaborate only through a mediator object.

Procedural Instructions

1. Identify Coupled Classes: Look for components that frequently call each other directly.
2. Declare Mediator Interface: Define a notify() method that components use to report events.
3. Implement Concrete Mediator: Centralize coordination logic. It stores references to all components and directs traffic between them.
4. Update Components: Components must only talk to the mediator, not to each other.

TypeScript Example

interface Mediator {
  notify(sender: object, event: string): void;
}

class Dialog implements Mediator {
  constructor(
    private button: Button,
    private textbox: Textbox,
  ) {
    this.button.setMediator(this);
  }
  notify(sender: object, event: string) {
    if (event === 'click') {
      /* Coordination logic here */
    }
  }
}

class Button {
  private mediator!: Mediator;
  setMediator(m: Mediator) {
    this.mediator = m;
  }
  click() {
    this.mediator.notify(this, 'click');
  }
}

Payoff

• Reusability: Individual components become easier to reuse as they are no longer tied to specific peers.
• SRP: Coordination logic is consolidated into one place.