Managing subscriptions

Subscriptions are a convenient way to read a value from a data stream to be used in your application logic. If unmanaged, they can create memory leaks in your application. A leaky application will end up consuming ever-increasing amounts of RAM, eventually leading the browser tab to become unresponsive, leading to a negative perception of your app and, even worse, potential data loss, which can frustrate end users.

In the current-weather component, we inject weatherSevice so that we can access the currentWeather$ component of BehaviorSubject. In Angular, services are singletons, meaning when they are first created in memory, they're kept alive as long as the module they're a part of is in memory. From a practical perspective, this will mean that most services in your application will live in the memory for the lifetime of the application. However, the lifetime of a component may be much shorter and there could be multiple instances of the same...