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Reactive programming with cycle.js



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Reactive programming with cycle.js

  1. 1. Reactive programming with Cycle.js
  2. 2. HELLO! I am Luca Mezzalira Solutions Architect @ Massive Interactive Google Developer Expert on Web Technologies Community Manager of London JavaScript User Group
  3. 3. AGENDA ▸ Reactive programming ▸ Model - View - Intent ▸ Cycle.js
  5. 5. PROGRAMMING PARADIGMS FUNCTIONAL It is a declarative programming paradigm, which means programming is done with expressions. In functional code, the output value of a function depends only on the arguments that are input to the function, so calling a function f twice with the same value for an argument x will produce the same result f(x) each time. IMPERATIVE It is a programming paradigm that uses statements that change a program's state. In much the same way that the imperative mood in natural languages expresses commands, an imperative program consists of commands for the computer to perform. Imperative programming focuses on describing how a program operates. REACTIVE It is a programming paradigm oriented around data flows and the propagation of change. This means that it should be possible to express static or dynamic data flows with ease in the programming languages used, and that the underlying execution model will automatically propagate changes through the data flow.
  6. 6. Imperative vs Reactive
  9. 9. OBSERVER PATTERN The observer pattern is a software design pattern in which an object, called the subject, maintains a list of its dependents, called observers, and notifies them automatically of any state changes, usually by calling one of their methods. It is mainly used to implement distributed event handling systems.
  10. 10. ITERATOR PATTERN In object-oriented programming, the iterator pattern is a design pattern in which an iterator is used to traverse a container and access the container's elements. The iterator pattern decouples algorithms from containers
  11. 11. RxJS
  12. 12. “BACK-PRESSURE? WHAT?! Main obstacle when you approach for the first time Reactive Programming is the vocabulary. My first suggestion is to familiarise with the domain, a lot of concepts become way easier if you understand what they mean before you start to work with them. streams, hot observables, cold observables, marbles diagram, back-pressure, operators...
  13. 13. STREAMS A stream is a sequence of ongoing events ordered in time. It can emit three different things: a value (of some type), an error, or a "completed" signal. EVERYTHING CAN BE A STREAM
  14. 14. COLD OBSERVABLES Cold observables start running upon subscription: the observable sequence only starts pushing values to the observers when subscribe is called. Values are also not shared among subscribers.
  15. 15. HOT OBSERVABLES When an observer subscribes to a hot observable sequence, it will get all values in the stream that are emitted after it subscribes. The hot observable sequence is shared among all subscribers, and each subscriber is pushed the next value in the sequence.
  16. 16. OPERATORS ▸ Creating Observables ▸ Transforming Observables ▸ Filtering Observables ▸ Combining Observables ▸ Error Handling Operators ▸ Mathematical Operators ▸ Conditional Operators ▸ Connectable Observables Operators
  18. 18. 2. MODEL VIEW INTENT
  19. 19. Architectures Timeline 90s MVP 80s MVC 2005 MVVM 2013 FLUX 2009 DCI 2015 MVI
  21. 21. MVI RULES ▸ A module shouldn’t control any other module (controller in MVC) ▸ The only shared part between modules are observables ▸ Intent is a component with only one responsibility: It should interpret what the user is trying to do in terms of model updates, and export these "user intentions" as events
  22. 22. VIEW Input: data events from the Model. Output: a Virtual DOM rendering of the model, and raw user input events (such as clicks, keyboard typing, accelerometer events, etc). VIEW RENDERER
  23. 23. INTENT Input: raw user input events from the View. Output: model-friendly user intention events. INTENT
  24. 24. MODEL Input: user interaction events from the Intent. Output: data events. MODEL
  25. 25. MVI PROs ▸ Better separation of concern ▸ Monodirectional flow ▸ Dependency Injection ▸ Applications become easier to test (in particular views) ▸ All the states live inside the Model and the View is state- agnostic
  26. 26. 3. Cycle.js
  27. 27. Cycle.js Cycle’s core abstraction is your application as a pure function main() where inputs are read effects (sources) from the external world and outputs (sinks) are write effects to affect the external world. These side effects in the external world are managed by drivers: plugins that handle DOM effects, HTTP effects, etc.
  28. 28. CORE CONCEPTS ▸ Objects ▸ Functions ▸ Drivers ▸ Helpers
  29. 29. DRIVERS Drivers are functions that listen to Observable sinks (their input), perform imperative side effects, and may return Observable sources (their output). Cycle.js DOMDriver
  30. 30. Cycle.js in action
  31. 31.
  32. 32. Why not using Reactive Programming in any project then?
  33. 33. THANKS EVERYONE Q&A @lucamezzalira