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What is Scala?

Scala is a modern language not unlike Groovy.
It is said to be more powerful (and faster) than Groovy or Rails which has been the reason for its adoption at sites like Twitter.

Many of its features and paradigms favor multi-threaded and concurrent development which may not be unfamiliar to Objective-C and WebObjects developers. Here's a summary:

 

Objective-C

Java

Scala

Mutable/Immuable Datatypes

Collections e.g: NSArray/NSMutableArray

No

All datatypes

Closures

Blocks (Extension)

No

Built-in

Static variables

Yes

Yes

No

Static methods/functions

Yes

Yes

No

Concurrency

Grand Central Dispatch (Extension)

Threads

Actors

 

Weakly Typed

Strongly Typed

Strongly Typed

Other notable features include:

 

Objective-C

Java

Scala

Parametered methods

Yes e.g: addObject: to:

No

Yes e.g: add(object= ,to=)

Class composition

Categories

Interfaces

Traits

A fuller description of Scala can be found here.

Why Use Scala?

With Web 2.0, building concurrent WebObjects applications is a must.
Developing and maintaining a concurrent or multi-threaded WebObjects application can be challenging.

Scala offers concurrency that is (effectively) built-in to the language and is inherently thread-safe.
So it may offer new solutions for concurrency in WebObjects.

Can WebObjects be Programmed In Scala?

Yes. It is very simple.
Scala compiles to java bytecode. Hence using it with WebObjects is fairly straightforward.

WebObjects In Scala

The following is an in-depth explanation of differences between Java and Scala in WebObjects:

EOs in Scala

Constants

Scala doesn't have static variables or methods. However, every class does have a Companion Object

In Java:

public class _Talent extends EOGenericRecord {
	public static final String ENTITY_NAME	= "Talent";

In Scala:

object _Talent extends  EOGenericRecord {
	val ENTITY_NAME = "Talent"

Compacted imports

What is five lines in Java:

import com.webobjects.eocontrol.EOGenericRecord;
import com.webobjects.eocontrol.EORelationshipManipulation;
import com.webobjects.foundation.NSArray;
import com.webobjects.foundation.NSData;
import org.apache.log4j.Logger;

Is three lines in Scala:

import com.webobjects.eocontrol.{EOGenericRecord, EORelationshipManipulation}
import com.webobjects.foundation.{NSArray, NSData}
import org.apache.log4j.Logger

How to Program WebObjects In Scala

  1. Install the Scala eclipse IDE
  2. Add Scala support to your WO project:
    1. Right-click your project in the WO Explorer
    2. In the context menu select Configure -> Add Scala Nature
  3. Convert to or use .scala instead of .java source

Note

This is for Eclipse/WOLips IDE

WO Scala Example

The following is a mixed Java/Scala version of the WO Movies D2W app.
All the EO logic and WO components are in Scala.
Only the Application class is Java.

No files shared here yet.

Setup

  1. Install and run the OpenBase OBMovies database.
  2. Right-click on Application.java and run as a WOApplication (as usual).

EO Templates

See: Scala templates

When you create your .eogen file, be sure to make the following changes in the EOGenerator Editor:

  1. Change the File Names Extension to "scala"
  2. Uncheck Java under Options
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