Changes for page WebObjects with Scala

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Author

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1		-XWiki.rmendis
	1	+XWiki.johnthuss

Content

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1	1	=== What is Scala? ===
2	2
3		-[[Scala>>http://en.wikipedia.org/wiki/Scala_(programming_language)]] is a language for concurrent computing.
	3	+[[Scala>>http://en.wikipedia.org/wiki/Scala_(programming_language)]] is a JVM language that is a hybrid of Object-Oriented and Functional styles.  It is useful as complete general purpose replacement for Java.  But its built-in Actors library makes it especially attractive for concurrent computing.
4	4	In this day and age of multi-core processors, concurrent computing can't be ignored.
5	5
6		-Many of Scala's features have been designed with concurrency in mind.
	6	+Many of Scala's features have been designed with concurrency in mind, primarily a preference for immutability and the use of other functional language paradigms.
7	7	Some of these may not be unfamiliar to Objective-C or WebObjects developers.
8	8
9	9	Here's a quick summary:
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24	24
25	25	=== Why Use Scala? ===
26	26
27		-Scala is inherently thread-safe.
28		-It has concurrency that is effectively built-in to the language.
	27	+Scala can help you to write thread-safe code.
	28	+It has concurrency that is built-in to the standard library, primarily via Actors.
29	29
30	30	So for WebObjects developers, Scala offers itself as a powerful, safe and easy-to-use solution for [[concurrent applications>>Building Concurrent Applications with WebObjects and Scala]]. (In other words, Scala Actors can be used for problems that would have normally required threads).
31	31
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42	42
43	43	=== Thread-Safe Shared Vars ===
44	44
45		-Scala doesn't have static variables or methods. Instead Scala employs the [[Singleton Pattern>>http://en.wikipedia.org/wiki/Singleton_pattern]] which is built into the language and is **thread-safe**: a class can have a //Companion Object// that will allow you to achieve something equivalent to static variables - but better.
	45	+Scala doesn't have static variables or methods. Instead Scala employs the [[Singleton Pattern>>http://en.wikipedia.org/wiki/Singleton_pattern]] which is built into the language and is **thread-safe**: a class can have a //Companion Object// that will allow you to achieve something equivalent to static variables - but better. Is this true?  I don't think Scala "object" instances (with the object keyword) are guaranteed to be thread-safe; they are just singletons
46	46
47	47	So you don't have to worry about synchronizing access to shared mutable fields in a concurrent application.
48	48
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188	188
189	189	== How to Use Scala Collections with EOF ==
190	190
191		-One of the benefits of Scala is its very powerful, concurrency-ready collection classes - primarily ##List##, ##Map## and ##Set##.
192		-Employing these instead of ##NSArray## and ##NSDictionary## in WebObjects/EOF may be challenging.
	191	+To use the Scala Collections API with an NSArray or NSDictionary you simply need to add an import:import scala.collection.JavaConversions.
193	193
194		-But one may modify the EO templates to produce API such as:
	193	+Then you can access the typical Scala collection methods directly on NSArray.  This employs a feature of Scala known as implicit conversions to automagically cast a NSArray (a Java Iterable) into a Scala Iterable while leaving the actual object unchanged.  Alternatively, you could generate an actual new scala.List instance by calling myNSArray.toList.
195	195
196		-{{code}}
197		-
198		-import scala.collection.JavaConversions._
199		-
200		-def movies = {
201		- storedValueForKey(_Studio.Keys.MOVIES).asInstanceOf[NSArray[Movie]]
202		-}
203		-
204		-def moviesList = {
205		- movies.asInstanceOf[java.lang.Iterable[Movie]].toList
206		-}
207		-
208		-{{/code}}
209		-
210		-This employs a feature of Scala known as **implicit conversions** to automagically convert a NSArray (a Java Iterable) into a Scala Iterable.
211		-
212	212	== How to Add Scala to a WO Project ==
213	213
214	214	{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
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234	234	1. [[Install the Scala eclipse IDE>>http://www.scala-ide.org/]]
235	235	1. Right-click on Application.java and run as a WOApplication (as usual).
236	236
	220	+Application can be made into a Scala class as well, but then you will have to create a launcher in Eclipse manually.
	221	+
237	237	== EO Templates ==
238	238
239	239	When you create your ##.eogen## file, be sure to make the following changes in the EOGenerator Editor: