Scala for android

Do More with Less:
Building Android Apps with Scala
Tony Hillerson • Tack Mobile
AnDevCon III
@thillerson @tackmobile

PRESENTATION ANDEVCON • MAY 14, 2012

ABOUT ME

Tony Hillerson
Software Architect & Partner Mobile design and development
company based in Denver, CO.
• O’Reilly Screencasts
• Computer Nerd @tackmobile
• Co-creator of FieldTest tackmobile.com

@thillerson
tony@tackmobile.com

PRESENTATION tackmobile.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


“ Learn one new
language per year
- The Pragmatic Programmers


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


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


Scala with Android


SBT
• Build tool (use for Java too)
• 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


But I Need My Eclipse!

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


Scala’s Features
and 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
class UnlessClass[T](block: => T) {
def unless(b: Boolean): Unit = {
if (!b) block
}
}

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

...
foo unless flag

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

Resources


Books on Scala
• http://www.scala-lang.org/node/959


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


Assembla

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


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


Thank You
@thillerson @tackmobile


Scala for android

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