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Getting Started with RxKotlin in Android Hello RxKotlin raywenderlichcom
>> YOUR LINK HERE: ___ http://youtube.com/watch?v=jnow3CCqs1Q
This video gives you an overview of RxKotlin and why or why not you should use it. • View the playlist here: • • RxKotlin • View the episode here: • https://www.raywenderlich.com/7419-be... • View the complete course here: • https://www.raywenderlich.com/7419-be... • --- • About www.raywenderlich.com: • https://www.raywenderlich.com/384-rea... • raywenderlich.com is a website focused on developing high quality programming tutorials. Our goal is to take the coolest and most challenging topics and make them easy for everyone to learn – so we can all make amazing apps. • We are also focused on developing a strong community. Our goal is to help each other reach our dreams through friendship and cooperation. As you can see below, a bunch of us have joined forces to make this happen: authors, editors, subject matter experts, app reviewers, and most importantly our amazing readers! • --- • From raywenderlich.com: • Reactive programming is not just another API. It’s a whole new paradigm and a very useful one. RxJava is a reactive implementation used on Android. Android is a perfect place to start your exploration of the reactive world. It’s made even easier with RxAndroid, a library that wraps asynchronous UI events to be more RxJava like. • Don’t be scared — I’ll bet the basic concept of reactive programming is known to you even if you are not aware of it yet. :] • Before creating your first observable, indulge yourself with a bit of a theory first. :] • In imperative programming, an expression is evaluated once and a value is assigned to a variable. • On the other hand, reactive programming is all about responding to value changes. • You have probably done some reactive programming — even if you didn’t realize it at the time. • Defining cell values in spreadsheets is similar to defining variables in imperative programming. • Defining cell expressions in spreadsheets is similar to defining and operating on observables in reactive programming. • The spreadsheet assigns cell B1 with a value of 2, cell B2 with a value of 3 and a third cell, B3, with an expression that multiplies the value of B1 by the value of B2. When the value of either of the the components referenced in the expression changes, the change is observed and the expression is re-evaluated automagically in B3: • As you probably know, it’s possible to use Java libraries in Kotlin projects thanks to Kotlin’s language compatibility with Java. If that’s the case, then why was RxKotlin created in the first place? RxKotlin is a Kotlin wrapper around RxJava, which also provides plenty of quite useful extension functions. Effectively, RxKotlin makes working with RxJava more Kotlin-y. • In this article, we’ll focus on using RxJava, since it’s critical to understand the core concepts of this approach, however everything you will learn applies to RxKotlin as well. • In the Observer pattern, you have objects that implement two key RxJava interfaces: Observable and Observer. When an Observable changes state, all Observer objects subscribed to it are notified. • Among the methods in the Observable interface is subscribe(), which an Observer will call to begin the subscription. • From that point, the Observer interface has three methods which the Observable calls as needed: • onNext(T value) provides a new item of type T to the Observer • onComplete() notifies the Observer that the Observable has finished sending items • onError(Throwable e) notifies the Observer that the Observable has experienced an error • As a rule, a well-behaved Observable emits zero or more items that could be followed by either completion or error. • That sounds complicated, but some marble diagrams may clear things up. • The circle represents an item that has been emitted from the observable and the black block represents a completion or error. Take, for example, a network request observable. The request usually emits a single item (response) and immediately completes. • A mouse movement observable would emit mouse coordinates but will never complete: • Here you can see multiple items that have been emitted but no block showing the mouse has completed or raised an error. • No more items can be emitted after an observable has completed. Here’s an example of a misbehaving observable that violates the Observable contract: • That’s a bad, bad observable because it violates the Observable contract by emitting an item after it signaled completion. • How to Create an Observable • There are many libraries to help you create observables from almost any type of event. However, sometimes you just need to roll your own. Besides, it’s a great way to learn!
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