Changes for page WebObjects with Scala

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1	1	=== What is Scala? ===
2	2
3		-[[Scala>>http://www.scala-lang.org/]] is a modern, multi-paradigm JVM language that is most often compared to [[Groovy>>http://en.wikipedia.org/wiki/Groovy_(programming_language)]], [[Clojure>>http://en.wikipedia.org/wiki/Clojure]] or [[Erlang>>http://en.wikipedia.org/wiki/Erlang_(programming_language)]]. Its [[functional language>>http://en.wikipedia.org/wiki/Functional_programming]] foundations and built-in [[Actors>>http://en.wikipedia.org/wiki/Actor_model]] library make it especially attractive for concurrent computing. (Scala is an abbreviation for "scalable" hinting at its design goals). In this day and age of multi-core processors concurrent computing can not be ignored.
	3	+[[Scala>>http://en.wikipedia.org/wiki/Scala_(programming_language)]] is a language for concurrent computing.
	4	+In this day and age of multi-core processors, concurrent computing can't be ignored.
4	4
5		-Many of the design features of Scala have been chosen with concurrency in mind, some of which may not be unfamiliar to Objective-C or WebObjects developers. Here's a summary:
	6	+Many of Scala's features have been designed with concurrency in mind.
	7	+Some of these may not be unfamiliar to Objective-C or WebObjects developers.
6	6
	9	+Here's a quick summary:
	10	+
7	7	|= |= Objective-C |= Java |= Scala
8		-|= Immutability | Partial - via collections //e.g: NSArray/NSMutableArray// | No | Yes
9		-|= Closures | Yes - via Blocks (//Extension//) | No | Yes - via Anonymous Functions
	12	+|= Separation of Mutable & Immuable Datatypes | Collections //e.g: NSArray/NSMutableArray// | No | Yes
	13	+|= Closures | Blocks (//Extension//) | No | Anonymous Functions
10	10	|= Static variables | Yes | Yes | No
11	11	|= Static methods or functions | Yes | Yes | No
12		-|= Concurrency | Yes - via [[Grand Central Dispatch>>http://en.wikipedia.org/wiki/Grand_Central_Dispatch]] (//Extension//) | //Yes - via Threads// | Yes - via [[Actors>>http://en.wikipedia.org/wiki/Actor_model]]
	16	+|= Concurrency | [[Grand Central Dispatch>>http://en.wikipedia.org/wiki/Grand_Central_Dispatch]] (//Extension//) | //Threads// | [[Actors>>http://en.wikipedia.org/wiki/Actor_model]]
13	13	|= |= Weakly Typed |= --Strongly Typed-- |= Strongly Typed
14	14
15	15	Other notable features include:
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16	16
17	17	|= |= Objective-C |= Java |= Scala
18	18	|= Parametered methods | Yes //e.g: addObject: to~:// | No | Yes //e.g: add(object= ,to=)//
19		-|= Class composition | Yes - via Categories | Yes - via Interfaces | Yes - via [[Traits>>http://en.wikipedia.org/wiki/Trait_(computer_science)]]
	23	+|= Class composition | Categories | Interfaces | Traits
20	20
21	21	=== Why Use Scala? ===
22	22
23		-For WebObjects developers, Scala offers itself as a powerful, safe and easy-to-use solution for [[concurrent computing>>Building Concurrent Applications with WebObjects and Scala]]. (In other words, Scala Actors can be used for problems that would have normally required threads).
	27	+Scala is inherently thread-safe.
	28	+It has concurrency that is effectively built-in to the language.
24	24
	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	+
25	25	=== Can WebObjects be Programmed In Scala? ===
26	26
27	27	Yes. It is very simple.
28		-By virtue of being a JVM-language, Scala compiles to java bytecode.
	35	+Scala compiles to java bytecode. Hence using it with WebObjects is fairly straightforward.
29	29
30		-Furthermore, being a multi-paradigm language grants Scala easy WebObjects-interoperability.
31		-
32		-===== Caveats =====
33		-
34		-Legacy tool support is often cited as a weak point. The [[Eclipse Scala plugin>>http://www.scala-ide.org]] has been found to be slow at times and sometimes buggy.
35		-
36	36	= WebObjects In Scala =
37	37
38	38	The following highlights some of the differences between Java and Scala in WebObjects:
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43	43
44	44	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	45
46		-You don't have to worry about synchronizing access to shared mutable fields in a concurrent application.
47		-(This is not however true when for example you have a ##val## declared as a ##NSMutableArray##. You will still have to synchronize when adding to or removing from this mutable field).
	47	+So you don't have to worry about synchronizing access to shared mutable fields in a concurrent application.
48	48
49	49	The following is an example of the use of a //Companion Object// for Talent in Scala instead of Talent static fields in Java.
50	50
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61	61
62	62	{{code}}
63	63
64		-object Talent {
	64	+object Talent extends EOGenericRecord {
65	65	val ENTITY_NAME = "Talent"
66	66
67	67	{{/code}}
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76	76
77	77	==== Compacted imports ====
78	78
	79	+Two lines in Java are compacted into one in Scala.
	80	+
79	79	In Java:
80	80
81	81	{{code value="java"}}
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186	186
187	187	== How to Use Scala Collections with EOF ==
188	188
189		-To use the Scala Collections API with an NSArray or NSDictionary you simply need to add an import:
	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.
190	190
191		-{{code value="java"}}
	194	+But one may modify the EO templates to produce API such as:
192	192
	196	+{{code}}
	197	+
193	193	import scala.collection.JavaConversions._
194	194
	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	+
195	195	{{/code}}
196	196
197		-After that, you may 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.
	210	+This employs a feature of Scala known as **implicit conversions** to automagically convert a NSArray (a Java Iterable) into a Scala Iterable.
198	198
199		-== How to Add Scala to a WO Project (in Eclipse) ==
	212	+== How to Add Scala to a WO Project ==
200	200
201	201	{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
202	202
	216	+{{note}}
	217	+
	218	+This is for Eclipse/WOLips IDE
	219	+
	220	+{{/note}}
	221	+
203	203	== WO Scala Example ==
204	204
205	205	The following example is an almost 100% Scala WO app. In reality it is a mixed Java/Scala app:
206	206	All the EO logic and WO components are in Scala.
207		-Only the Application class remains Java.
	226	+Only the Application class is Java.
208	208
209	209	It is based on the D2W Movies example.
210	210
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215	215	1. [[Install the Scala eclipse IDE>>http://www.scala-ide.org/]]
216	216	1. Right-click on Application.java and run as a WOApplication (as usual).
217	217
218		-{{note}}
219		-
220		-Application can be made into a Scala class as well, but then you will have to create a launcher in Eclipse manually.
221		-
222		-{{/note}}
223		-
224	224	== EO Templates ==
225	225
226	226	When you create your ##.eogen## file, be sure to make the following changes in the EOGenerator Editor: