Module 05 - RxJS, Http and Pipes


[fun-with-rxjs]	Introduction to rxjs main classes and concepts

We understood the meaning of a Stream
We defined what an Observer<T> is and understood that it has 3 methods
- next(T)
- complete()
- error(err)
We understood that Observable<T> is an object that allows observers to subscribe
- subscribe(Observer<T>)
We saw how to define an observer explicitly by supplying the 3 methods and their implementation
We saw how to create an observable using the interval operator
We saw that 2 observers that subscribe on different times, get different sets of events that are not synchronized
We understoof the difference between cold observables and hot observables
We have seen a few other factory operators:
- timer - creates an observable with time delay. It has two variations
  - timer(----)=> ----0|
  - timer(----, --) => ----0--1--2--3--4...
- of - wraps a value or values inside a synchronous observable
  - of(42) => (42)|
  - of(1, 2, 3) => 123|
- from - serves as a multifunction converter between any wrapper to observable
  - from([1, 2, 3]) => [1, 2, 3]|
  - from(Promise ----42|) => ----42|
We saw how to create a custom observable using the observable constructor
We got familiar with the Subject object and understood that it is a hot observable
We saw that a subject can be used as a proxy to "heat" a cold observable
We learned about BehaviorSubject and understood that it is just a subject that sends the latest event to a new observer on the moment of subscription

We learned how to develop stateful services using BehaviorSubject and expose it as an observable using the .asObservable() method
We understood that if we subscribe to an observable we must also unsubscribe from it when we are done with it to avoid memory leaks
We saw that we can bind directly to an observable using the async pipe in the html
We learned the term Fully Reactive Application as one where we pass observables all the way from the services to the html templates
We saw how to configure manual change detection for components and understood that it can dramatically improve performance
We saw how to inject the ChangeDetectorRef and to manually activate detectChanges to force invalidation of the DOM

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