This unit focuses on two design patterns: Observer and Strategy. We'll use these patterns to enable responsive security and flexible climate control in our smart home system.

1. Observer Pattern:

   • Purpose: Allows an object (observer) to watch another (subject) and be notified of changes.
   • Steps:
     • Define a Subject class with registration, unregistration, and notification methods (e.g., for a SecuritySystem).
     • Implement observer interfaces or abstract classes that react to changes (e.g., SecurityApp, SecurityLight).

2. Strategy Pattern:

   • Purpose: Defines a family of algorithms and makes them interchangeable.
   • Steps:
     • Define a strategy interface or abstract class with a method for the desired behavior (e.g., TemperatureControlStrategy for controlling temperature).
     • Implement specific strategies with concrete behaviors (e.g., HeatingStrategy, CoolingStrategy).
     • Create a context to use and switch strategies (e.g., a ClimateControl system).

Here is the complete code to implement the Observer pattern using TypeScript:

The securitySystem instance notifies both SecurityApp and SecurityLight when the state changes to "Intrusion Detected."

Here is the complete code to implement the Strategy pattern using TypeScript:

The ClimateControl instance can switch between HeatingStrategy and CoolingStrategy to control the temperature accordingly.

By implementing the Observer and Strategy patterns, our smart home system becomes more robust and versatile. The Observer pattern ensures that our security system is responsive by notifying observers of changes, while the Strategy pattern provides flexibility to our climate control system by allowing different temperature control strategies to be used interchangeably. This combination leads to a more adaptable and efficient smart home environment.