Neither does: const mappedObservable = doBitmap(). Thus, to reemphasize: const bitmapObservable = doBitmap() ĭoes nothing but return an Observable, but doesn’t start production of a bitmap. This was a source of confusion for me, map and its kin can be thought of a formula or a description of what will happen later, when we actually subscribe to the underlying source. This is a style of programming akin to using venerable jQuery's finders or Ruby-on-Rail’s ActiveRecord’s filters.Īnd note that most of the operators do not cause a subscription. So the original observable remains unchanged. So if we replace map with flatMap and run again:Īs an aside, what do map, flatMap and switchMap return? The simple answer is that almost all the operators take in an Observable and return a new Observable. Internally, every time our function returns an Observable the flatMap subscribes each one and sends the data that they produce down the line. Much like array.map (which maps an array to another array) is analogous to array.flatMap (which maps an array of arrays to a “flat” array), observable.flatMap takes an “Observable which produces Observables” and maps it down to the data elements produced just like a “flat” Observable. class Bitmap ) īut Reactive libraries provide a much easier way: Enter 'flatMap’ After the bitmap is generated a dialog pops up that awaits user confirmation.įirst we add some HTML to the HTML section to import the RxJS library Īnd start adding some Javascript and create a dummy class that we will “produce”.Because the generation takes some time, there is a “Cancel” button that can be used to stop the process.The user starts the process by clicking on a “Start” button.We are implementing the feature in our app that generates a bitmap of the collage and then asks the user for confirmation that he wants to share it. But because all the language variants ReactiveX follow and implement the same concepts and naming conventions, hopefully this should be helpful in its usage in other languages (of which there are many, Ruby, Swift, Java, etc).
#JAIME CHAM PICCOLLAGE CODE#
The code should be understandable with a cursory familiarity with modern Javascript and doesn’t presume knowledge of the “ ReactiveRx” framework (or its Javascript variant RxJS) Reactive framework. In this tutorial we are going to apply the Reactive Programming techniques to a real life use case in our app PicCollage, and hopefully elucidate some benefits and gotchas of the approach.
A Gentle Introduction to Reactive Programming (via RxJS)
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