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WebObjects with Scala

Version 241.1 by Ravi Mendis on 2009/09/15 22:37
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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.

How to Develop 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 Scala -> Add Scala Nature
  3. Convert or use .scala instead of .java source
Warning

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.

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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