$ whoami

Mobile dev at Guestful

http://verybadalloc.com

@AnasAmbri

At Guestful

We make reservations for restaurants

• On a restaurant's website
• On a restaurant's FB page
• On our own website
• Through the mobile apps

Disclaimer

This talk is based on code used in the Android project

So, if you ever spot a bug, don't hesitate to let me know. Our users will thank you. KTHXBYE

Title ideas

• Add some Groove to your app

• Groovy App Development

• Android got the grooves

(too long)

(too simple)

(too cheesy)

There is an app for that

Basically, we are gonna write an Android app in Groovy to find a title for a talk about writing Android apps in Groovy

What is Groovy?

Dynamic optionally-typed 

def obj = someFunctionToTachQuack(zebra)
obj.quack()

Why Groovy?

Nice substitute to Java's verbosity and excessive OOP-ness

Hello World

println "Hello, world"

Groovy

public class HelloWorld {

    public static void main(String[] args) {
        System.out.println("Hello, World");
    }

}

Java

Another Example

elements = restaurants.sort({ Object a, b ->
    int distanceFromFirst = 
            DistanceCalculator.getDistanceInMeters(
                    location, 
                    new Coordinate(a.address.location.coordinates
                    )
            )
    int distanceFromSecond = 
            DistanceCalculator.getDistanceInMeters(
                    location, 
                    new Coordinate(b.address.location.coordinates
                    )
            )
    return distanceFromFirst <=> distanceFromSecond
    })

Groovy

Another Example (2)

public class RestaurantDistanceComparator implements Comparator<JsonObject> {
        private Coordinate location;
        public RestaurantDistanceComparator(Coordinate currentLocation) {
            this.location = currentLocation;
        }
        @Override
        public int compare(JsonObject jsonObject, JsonObject jsonObject2) {
            int distanceFromFirst = DistanceCalculator.getDistanceInMeters(
                    new Coordinate(jsonObject.getJsonObject("address")
                            .getJsonArray("coordinates")),
                    location
            );
            int distanceFromSecond = DistanceCalculator.getDistanceInMeters(
                    new Coordinate(jsonObject2.getJsonObject("address")
                            .getJsonArray("coordinates")),
                    location
            );
            return distanceFromFirst < distanceFromSecond? -1 : 1;
        }
    }

// FINALLY
Collections.sort(restaurants,
    new RestaurantDistanceComparator(location)
);

Java

Json Parsing

def response = 
    new JsonSlurper().parse(bytes, "utf-8")
callback.onSuccess(response.results)

Groovy

Java

0) Figure out whether you need to 
  need models or not
If yes ==> 
1) Choose among these libraries:
            - Gson
            - Jackson

2) Create a lot of files, 
   with models for each object you
    will ever exchange with your backend.

3) Give up on programming

If no ==> 
1) Consider using Java's JSONObject.
   
2) Find out it has the worst 
   implementation ever
   because of its constant try-catch.

3) Try javax.json
 and Discover its getJsonObject syntax

4) Give up on programming

Demo

Probably the first time someone does a code demo on one leg

Summary

Step 0: Install groovy-2.4.0

//On OSX/Linux
$ curl -s get.gvmtool.net | bash
$ gvm install groovy 2.4.0-beta-3




//On Windows
Switch to Linux

Or

Go here: http://groovy.codehaus.org/Download
Then switch to Linux

Summary

buildscript {
    repositories {
        mavenCentral()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.12.2'
        //Add plugin
        classpath 'me.champeau.gradle:gradle-groovy-android-plugin:0.3.0'
    }
}
apply plugin: 'android'
//Apply it
apply plugin: 'me.champeau.gradle.groovy-android'

Step 1: Add groovy plugin

Summary

dependencies {
    compile 'org.codehaus.groovy:groovy:2.4.0-beta-3:grooid'
    //Only needed if using Groovy's Json
    compile ('org.codehaus.groovy:groovy-json:2.4.0-beta-3') {transitive = false}
}

Step 2: Add groovy compiler as dependency

When can I use this?

It depends...

Short Answer

For your boss' project, NO

For your own project, go crazy!

Shortcomings

Loose typing = higher method count

• In debug, about 20k methods
• In release, you can use Proguard

Shortcomings

Still in beta = some bugs

For example, can't include the public interface defined in a base class in a derived class

Shortcomings

No joint compilation (yet)

If you liked what you saw

Try Kotlin