This document summarizes a presentation about React Native, a library for building mobile apps using JavaScript and React. React Native allows building native mobile apps using the same tools and workflow as web development. It brings the "React way" of building UIs with reusable components to mobile and uses a single-direction data flow. While code can be shared between platforms, some UI components may not be fully reusable due to platform differences. The virtual DOM generated by components is translated to real native UI.

1. React Native
Unleash the power of
react in your device
AMSTERDAM 11-12 MAY 2016
This work is licensed under a Creative Commons Attribution 4.0
International License

2. HELLO!I am Eduard Tomàs 
You can find me at @eiximenis
I work @ PlainConcepts
http://www.plainconcepts.com

3. What is React
Native?
And what makes it different?

4. That have native UI
React Native is a
library to build
mobile apps
Using JavaScript and
the same workflow and
tools that we use to
build web applications

5. What makes React Native fresh and powerful is…
But these are’nt
the most
important things…

6. React Native
brings the “React
way” to mobile
development

7. “Thinking in
React”

8. Only components
Single source of truth
One direction data flow

9. Reusable Stateless
Components
Avoiding state in your
components not only make
them reusable… also can
save your life!
State should be stored in a
single point.
Components should have only
“read acces” to this state
Components should expose
an API to change its behavior

10. React Native
architecture

11. Not a “write
once” solution
At least not yet!
JavaScript code can be
shared with iOS and Android
applications
UI code (React components)
is not totally reusable.
Most components are shared
between platforms but some
does’nt
This is improving

12. UI is fully native
Virtual DOM generated by
components is translated to
real native UI
components.
A react native button is
really a UIButton or a
android.widget.Button

13. And about
JavaScript…
JavaScript is bundled in the
application package
JavaScript is executed
using JavaScript Core (part
of WebKit project)
JavaScript runs in an
Asynchronous way…
… with native methods
calls batched…
… exchanging serializable
messages (not sharing
mutable data)

14. What about
styling?
React Native contains a custom implementation of
CSS
Based on JavaScript objects (no CSS files exist)

16. What about
layouts?
Layout in Android and iOS differs a lot
React Native relies on its own layout system
Basic implementation of CSS flexbox standard

17. “Functional” UI

18. f is a pure function A pure function is a
function with no
side effects
𝑈𝐼 = 𝑓 𝑑𝑎𝑡𝑎

20. 𝑈𝐼 = 𝑓 𝑐𝑜𝑢𝑛𝑡

21. 𝑈𝐼 = 𝑓 𝑐𝑜𝑢𝑛𝑡 =
𝑑𝑖𝑣(
𝑠𝑝𝑎𝑛 ′𝐶𝑜𝑢𝑛𝑡′
+ 𝑐𝑜𝑢𝑛𝑡
𝑏𝑢𝑡𝑡𝑜𝑛 ′𝐴𝑑𝑑 + 1′
)

24. Previous code was from a web
project. In mobile <div> and <span>
mean nothing but same principles
apply.
Only component names change
From web
to mobile

26. Updating the
state
State should be on a single
place, usually in the “top
most” component

28. CounterPage
TopMost component
holding state
Receives events from
Counter component and
updates its own state
Counter
Stateless component
Have “read only” view of
data in their props
Communicates via events
One direction data flow

29. WANT BIG IMPACT?
USE BIG
IMAGE.
Time to code…

30. The “mobile
workflow”
Code something
Compile
Deploy on emulator
Do some changes
Compile again
Deploy again
And again, and again…

31. The “React Native
Workflow”
Code something
Deploy on emulator
Do some changes
Refresh on emulator
Never deploy again
Just change code and
refresh

32. The debugging
experience
Debugging code is
performed through Chrome
As any web application

33. Navigation
React Native offers one top
most component
(Navigator) to handle
application navigation
Offers an API similar to the
HTML5 PushState.
Each scene (screen) is a
top react component

34. WANT BIG IMPACT?
USE BIG
IMAGE.
Show me in action!

35. React Native APIs
React Native come with a
lot of APIs to do basic stuff
Most of these APIs exists
for both Android and iOS

36. AppState: manages the application state and notifies
changes
AsyncStorage: Persistent key/value storage
CameraRoll: Provides access to local camera roll or gallery
Vibration: Access to the underlying vibration API
fetch: API for performing HTTP Requests. Mimics the same
API available in some browsers (i. e. Chrome)
GeoLocation: API for accessing the geo location data.
Mimics the same HTML5 API.
…

37. Q: Can I interoperate
with native code?
Yes, you can create a
native module using ObjC
(for iOS) or Java (for
Android)
A native module is a class
For iOS must to conform the
RCTBridgeModule protocol
For Anrdoid must extend
ReactContextBaseJavaModule
class

38. Q: Can I use native
UI controls?
Yes, you can expose native
UI controls to JavaScript
You can bridge native
properties to/from
JavaScript code
Can dispatch events from the UI
control to JavaScript code

39. Any questions?
You can find me at @eiximenis or contact me using
etomas@plainconcepts.com

40. Thanks!

41. Info@plainconcepts.com
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08029 Barcelona, España
+34 93 3607 114
Barcelona