Difference between observable and observer in angular 2
Answers
Answer:
When version 2 of Angular came out, it introduced us to observables. The Observable isn’t an Angular specific feature, but a new standard for managing async data that will be included in the ES7 release. Angular uses observables extensively in the event system and the HTTP service. Getting your head around observables can be quite a thing, therefore i’m here to explain it the easy way.
Observables
Observables are lazy collections of multiple values over time.
yeah, right…well, actually it’s pretty easy:
Observables are lazy
You could think of lazy observables as newsletters. For each subscriber a new newsletter is created. They are then only send to those people, and not to anyone else.
Observables can have multiple values over time
Now if you keep that subscription to the newsletter open, you will get a new one every once and a while. The sender decides when you get it but all you have to do is just wait until it comes straight into your inbox.
If you come from the world of promises this is a key difference as promises always return only one value. Another thing is that observables are cancelable. If you don’t want your newsletter anymore, you unsubscribe. With promises this is different, you can’t cancel a promise. If the promise is handed to you, the process that will produce that promise’s resolution is already underway, and you generally don’t have access to prevent that promise’s resolution from executing.
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Answer:
Angular uses the Observer pattern which simply means — Observable objects are registered, and other objects observe (in Angular using the subscribe method) them and take action when the observable object is acted on in some way. They are similar to promises, but with some differences.
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