Scala for android

PRESENTATION ANDEVCON • MAY 14, 2012

Do More with Less:Building Android Apps with ScalaTony Hillerson • Tack Mobile

AnDevCon III

@thillerson @tackmobile

PRESENTATION tackmobile.com

ABOUT ME

Tony HillersonSoftware Architect & Partner

• O’Reilly Screencasts• Computer Nerd• Co-creator of FieldTest

@[email protected]

Mobile design and development company based in Denver, CO.

@tackmobiletackmobile.com


Why Would I Consider Scala?

• Write less boilerplate code• More powerful features than Java• Move towards Functional paradigms


N.B. I Am Not a Scala Expert

• You can probably stump me• This talk is about how you can explore what

Scala might do for you


My Goals

• Introduce you to Scala• Introduce you to Scala with Android• Give you a few good reasons to use Scala• Encourage you to become a Polyglot


Be a Polyglot


“- The Pragmatic Programmers

Learn one new language per year


Seven Languages in Seven Weekshttp://pragprog.com/book/btlang/seven-languages-in-

seven-weeks

http://pragprog.com/book/btlang/seven-languages-in-seven-weeks







What is Scala?


What is Scala?

• JVM Language• Take advantage of any Java library• Bridges the divide between OO and

Functional spaces


scala-lang.org


REPL

• Read Execute Print Loop• Command line: scala• Test code quickly


Strongly, Statically Typed

• Compile time type checking• Restrictions on how types can be used

together• For comparison:

• Javascript - Weakly typed, Dynamic• Ruby - Strongly typed, Dynamic


≠ Boilerplate

• Perens are (sometimes) optional• Semicolons are (mostly) optional• Types are inferred, thus:

ArrayList<GameTileMotionDescriptor> descriptors = new ArrayList<GameTileMotionDescriptor>();

VS.val descriptors = new ArrayBuffer[GameTileMotionDescriptor]


More OO than Java

• Everything is an object• Operators are actually methods• For instance, override the “+” method


Functional Language

• Functions are first class citizens• High order functions: Functions that

operate on functions• Avoids mutable state• Could get pretty academic• Scala bridges the gap between OO and

Functional


A Javascript Function

var doSomething = function(data) { doSomethingElseWithData(data);}


A Scala Function

def doSomething(data:A):B = { doSomethingElseWithData(data)}


Concurrent

• Optional immutable state• Actors - Higher concept than Threads/

Thread Pools


Example Conversion Project


Slider Puzzle


Experiment: Convert from Java to Scala

• Android• https://github.com/thillerson/Android-Slider-Puzzle

• Scala• https://github.com/thillerson/scala-android-slider-puzzle

• Mixed results.

• I have a lot to learn about Scala

https://github.com/thillerson/Android-Slider-Puzzle

https://github.com/thillerson/Android-Slider-Puzzle

https://github.com/thillerson/scala-android-slider-puzzle

https://github.com/thillerson/scala-android-slider-puzzle


Mike Burns

• Thoughtbot• Android and Scala at Android Open• http://robots.thoughtbot.com/post/

5836463058/scala-a-better-java-for-android• Ohlaunch - https://github.com/mike-burns/

ohlaunch

http://robots.thoughtbot.com/post/5836463058/scala-a-better-java-for-android




https://github.com/mike-burns/ohlaunch





Scala with Android


SBT

• Build tool (use for Java too)• https://github.com/harrah/xsbt/wiki/

Getting-Started-Welcome

https://github.com/harrah/xsbt/wiki/Getting-Started-Welcome





android-plugin

• https://github.com/jberkel/android-plugin/wiki/getting-started

• ADB/DDMS Integration• Build and Release

https://github.com/jberkel/android-plugin/wiki/getting-started





But I Need My Eclipse!

• http://www.assembla.com/wiki/show/scala-ide/Developing_for_Android

http://www.assembla.com/wiki/show/scala-ide/Developing_for_Android





Scala’s Featuresand Idioms


vals and vars

• var - A variable definition. Required to be initialized when in a function

• val - A value definition. Once set, cannot be changed• Basically a “final”

• Important consideration for concurrent programming


Methods

• Declaration conventions• Suffix notation• Infix notation


Looping

• for ( item <- items )• ranges


Scala Collections

• Scala really shines on collections• A good introduction to functional power


Anonymous Function Syntax

• ( args ) => ReturnType• ( x:Int ) => x * x


Inheritance in Java

• Single Inheritance• Restricting!


Inheritance in C++

• Multiple Inheritance• Mind Blown


Traits

• Mixin pattern• Abstract/Interface + implementation


Extending the Language

http://naturalsoftware.blogspot.com/2009/05/ruby-unless-scala.html

class UnlessClass[T](block: => T) { def unless(b: Boolean): Unit = { if (!b) block }}

implicit deftoUnlessClass[T](block: => T): UnlessClass[T] = { new UnlessClass[T](block)}

...foo unless flag




Resources


Books on Scala

• http://www.scala-lang.org/node/959

http://www.scala-lang.org/node/959

http://www.scala-lang.org/node/959


Positronic

• Framework for Android in Scala• Makes use of Actors• http://rst.github.com/tutorial.html

http://rst.github.com/tutorial.html

http://rst.github.com/tutorial.html


Assembla

• http://www.assembla.com/wiki/show/scala-ide/Developing_for_Android






Seven Languages in Seven Weekshttp://pragprog.com/book/btlang/seven-languages-in-

seven-weeks








Recap

• Scala is perfect for Android• Consider expanding your mind• Be a Polyglot


Thank You@thillerson @tackmobile

Scala for android

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