Full Stack Scala

Full Stack Scala
Scala in the backend and frontend!
Ramnivas Laddad
Founder, Paya Labs
@ramnivas

@ramnivas
• Spring framework and Cloud Foundry
contributor
• Main interests
• Scala and functional programming
• Cloud computing
• Author of books and articles
• AspectJ in Action (1st and 2nd edition)
• Speaker at many professional conferences
• JavaOne, ScalaDays, JavaPolis, SpringOne, Software
Development, No Fluff Just Stuff, OSCON etc.

High-level Architecture
API Server Static Page Server
html, js, css,
…
GET, PUT, POST,
DELETE
{
"name" : ...
}

API Server
API Server Static Page Server
html, js, css,
…
GET, PUT, POST,
DELETE
{
"name" : ...
}

Backend Structure
DatabaseSendgrid

Backend Structure
DatabaseSendgridS3

Backend Structure
Database
Data Access Layer
SendgridS3

Backend Structure
Database
Data Access Layer
SendgridS3
Talk by Rob Norris
Programs asValues: JDBC Programming with Doobie

Backend Structure
Database
Data Access Layer
SendgridS3
Apache
Commons

Backend Structure
Database
Data Access Layer
SendgridS3
Apache
Commons
AWS
SDK

Backend Structure
Database
Data Access Layer
Service Layer
SendgridS3
Apache
Commons
AWS
SDK

Backend Structure
Database
Data Access Layer
Service Layer
HTTP Layer
SendgridS3
Apache
Commons
AWS
SDK

High-level Architecture
Static Page Server
html, js, css,
…
API Server
GET, PUT, POST,
DELETE
{
"name" : ...
}

Serving static contents
var express = require('express');
var fs = require('fs');
var app = express();
var port = process.env.PORT || 4000;
var devMode = process.env.SERVE_MODE != "SERVE_PROD";
var serveInfo = { dir: __dirname + ‘/dev-bin', maxAge: 0}
if (!devMode) {
var oneHour = 60*60*1000;
serveInfo = { dir: __dirname + ‘/prod-bin', maxAge: oneHour}
}
app.use(express.static(serveInfo.dir, { maxAge: serveInfo.maxAge }));
app.get('*', function(request, response, next) {
response.sendFile(serveInfo.dir + '/index.html');
});
app.listen(port, function() {
console.log("Started on " + port + " (dev mode = " + devMode + ")n");
});

Why Scala.js
Functional Programming

Choosing a UI Framework
Simple
Mental Model

Simple
Mental Model
Immutable
Data

Simple
Mental Model
Functional
programming
Immutable
Data

Simple
Mental Model
Mobile
Functional
programming
Immutable
Data

Simple
Mental Model
Mobile
Functional
programming
Immutable
Data
Isomorphism

Simple
Mental Model
CommunityMobile
Functional
programming
Immutable
Data
Isomorphism

What is React?
• “A JavaScript library for building user interfaces” by
Facebook
• Focuses just on the UI
• Uses virtual DOM
• One-way data-ﬂow

Frontend Overview
Router Flux
Component

Frontend Overview
Router
Store
Flux
Component

Frontend Overview
Router
Store
Flux
Component
Rest Client

Frontend Overview
ComponentRouter
Store
Flux
Component
Rest Client

Scala.js with React
• Statically-typed wrapper around React
• Fluent, builder API to create components
• Well-implemented router (v2)
scalajs-react

Simple Mental Model
View
PropertiesState

Mostly Immutable
ComponentRouter
Store
Flux
Component
Rest Client

Taking advantage of immutability
def shouldComponentUpdate(scope: ScopeType,
nextProps: P,
nextState: S) = {
scope.props != nextProps ||
scope.state != nextState
}

Flux Component
object ArtistRegistrationWrapper extends
FluxComponent[String, ArtistEditDto](Seq(ArtistStore, InstrumentStore)) {
def onArtistChange(artist: ArtistEditDto): Unit = {
ArtistUpdated(artist).dispatch()
}
...
def element(props: String) = {
...
div(
ArtistRegistration(
ArtistRegistrationProps(
artist, allInstruments, onArtistChange,
onArtistCoverPhotoChange, onArtistProfilsePhotoChange)
)
)
}
}

Component
object ArtistRegistration extends
Component[ArtistRegistrationProps] {
def element(props: ArtistRegistrationProps): ReactTag = {
div(…)
}
}

Responding to events
override def receive = {
case ArtistUpdated(newValue) =>
artist = newValue
emitChange()
case ArtistSaved =>
save()
emitChange()
...

No sweat undo/redo
trait CompositionStore extends AbstractStore {
val compositionStack = new UndoStack[Composition]()
override def receive = {
case NewComposition =>
compositionStack.clear()
loaded()
case LoadComposition(c) =>
compositionStack.clear()
compositionStack.push(c)
loaded()
case UpdateComposition(c) =>
compositionStack.push(c)
emitChange()
case UndoComposition =>
compositionStack.undo()
emitChange()
case RedoComposition =>
compositionStack.redo()
emitChange()
...
}

Mobile: React Native
https://facebook.github.io/react-native

Mobile: React Native
https://github.com/chandu0101/scalajs-react-native
https://facebook.github.io/react-native

Bridging Native React Components
• Problem:
• You got to use components developed in the
wild
• Requires signiﬁcant boilerplate to make it work
from scalajs-react
• Solution: Some macro magic!

Bridging Native React Components
• Problem:
• You got to use components developed in the
wild
• Requires signiﬁcant boilerplate to make it work
from scalajs-react
• Solution: Some macro magic!
github.com/payalabs/scalajs-react-bridge

Example Bridge Component
case class TagsInput(id: js.UndefOr[String] = js.undefined,
className: js.UndefOr[String] = js.undefined,
ref: js.UndefOr[String] = js.undefined,
key: js.UndefOr[Any] = js.undefined,
defaultValue: js.UndefOr[Seq[String]] = js.undefined,
value: js.UndefOr[Array[String]] = js.undefined,
placeholder: js.UndefOr[String] = js.undefined,
onChange: js.UndefOr[js.Array[String] => Unit] = js.undefined,
validate: js.UndefOr[String => Boolean] = js.undefined,
transform: js.UndefOr[String => String] = js.undefined)
extends ReactBridgeComponent

UsingTagsInput
div(
TagsInput(
defaultValue = Seq(“foo","bar"),
onChange = printSequence _
)
)

Using MDL in React
• Problem:
• Components need to be “upgraded”
• Solution:
• React wrapper component around a ReactTag
• Upgrades element upon mounting
• Implicits to avoid noise

Using MDL in React
• Problem:
• Components need to be “upgraded”
• Solution:
• React wrapper component around a ReactTag
• Upgrades element upon mounting
• Implicits to avoid noise
github.com/payalabs/scalajs-react-mdl

Example MDL Use
a(className := "mdl-button mdl-js-button
mdl-button--raised mdl-button—colored
mdl-js-ripple-effect",
onClick --> saveAction())("Save").material

Things on the Horizon
• GraphQL?
• Stitch?
• Relay?
• Falcor?

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