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).
	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		-In this day and age of multi-core processors concurrent computing can not be ignored. 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		-|= Static methods | 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]]
	15	+|= Static methods or functions | Yes | Yes | No
	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: