Changes for page WebObjects with Scala

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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.
4		-In this day and age of multi-core processors, concurrent computing can't be ignored.
	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.
5	5
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.
	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:
8	8
9		-Here's a quick summary:
	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
	10	+|= Static variables | Yes | Yes | No
	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]]
	13	+|= |= Weakly Typed |= --Strongly Typed-- |= Strongly Typed
10	10
11		-|= |= Objective-C |= Java |= Scala
12		-|= Separation of Mutable & Immuable Datatypes | Collections //e.g: NSArray/NSMutableArray// | No | Yes
13		-|= Closures | Blocks (//Extension//) | No | Anonymous Functions
14		-|= Static variables | Yes | Yes | No
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]]
17		-|= |= Weakly Typed |=--Strongly Typed--|= Strongly Typed
18		-
19	19	Other notable features include:
20	20
21		-|= |= Objective-C |= Java |= Scala
22		-|= Parametered methods | Yes //e.g: addObject: to~:// | No | Yes //e.g: add(object= ,to=)//
23		-|= Class composition | Categories | Interfaces | Traits
	17	+|= |= Objective-C |= Java |= Scala
	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)]]
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.
	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).
29	29
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		-
32	32	=== Can WebObjects be Programmed In Scala? ===
33	33
34	34	Yes. It is very simple.
35		-Scala compiles to java bytecode. Hence using it with WebObjects is fairly straightforward.
	28	+By virtue of being a JVM-language, Scala compiles to java bytecode.
36	36
	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	+
37	37	= WebObjects In Scala =
38	38
39	39	The following highlights some of the differences between Java and Scala in WebObjects:
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40	40
41	41	== EOs in Scala ==
42	42
43		-=== Thread-Safe Shared Vars ===
	42	+=== Thread-Safe Shared Vars ===
44	44
45		-Scala doesn't have static variables or methods. However, a class can have a //Companion Object// that will allow you to achieve something equivalent to static variables.
46		-One of the advantages of this approach is that it is **thread-safe**, so you don't have to worry about synchronizing access to these fields in a concurrent application.
	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.
47	47
	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).
	48	+
48	48	The following is an example of the use of a //Companion Object// for Talent in Scala instead of Talent static fields in Java.
49	49
50	50	Java:
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60	60
61	61	{{code}}
62	62
63		-object Talent extends EOGenericRecord {
	64	+object Talent {
64	64	val ENTITY_NAME = "Talent"
65	65
66	66	{{/code}}
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75	75
76	76	==== Compacted imports ====
77	77
78		-Two lines in Java are compacted into one in Scala.
79		-
80	80	In Java:
81	81
82	82	{{code value="java"}}
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165	165
166	166	An example of accessing variables in WebObjects with the following languages:
167	167
168		-|= |= Objective-C |= Java |= Scala
169		-|= getter | ##object name## | ##object.name()## | ##object.name##
170		-|= setter | ##object setName:aName## | ##object.setName(aName)## | ##object.name = aName##
	167	+|= |= Objective-C |= Java |= Scala
	168	+|= getter | ##object name## | ##object.name()## | ##object.name##
	169	+|= setter | ##object setName:aName## | ##object.setName(aName)## | ##object.name = aName##
171	171
172	172	Of course in Java, we may generate WebObjects classes with "get" methods as well in order to stick to convention.
173	173	In scala there is an additional convenience we may use to produce "get" and "set" methods in addition to the default Scala accessors - Scala Annotations.
...	...	@@ -187,38 +187,25 @@
187	187
188	188	== How to Use Scala Collections with EOF ==
189	189
190		-One of the benefits of Scala is its very powerful, concurrency-ready collection classes - primarily ##List##, ##Map## and ##Set##.
191		-Employing these instead of ##NSArray## and ##NSDictionary## in WebObjects/EOF may be challenging.
	189	+To use the Scala Collections API with an NSArray or NSDictionary you simply need to add an import:
192	192
193		-But one may modify the EO templates to produce API such as:
	191	+{{code value="java"}}
194	194
195		-{{code}}
	193	+import scala.collection.JavaConversions._
196	196
197		-def movies: NSArray[Studio] = {
198		- storedValueForKey(_Studio.Keys.MOVIES).asInstanceOf[NSArray[Studio]]
199		-}
200		-
201		-def moviesList: List[Studio] = {
202		- movies.objects.toList
203		-}
204		-
205	205	{{/code}}
206	206
207		-== How to Add Scala to a WO Project ==
	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.
208	208
	199	+== How to Add Scala to a WO Project (in Eclipse) ==
	200	+
209	209	{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
210	210
211		-{{note}}
212		-
213		-This is for Eclipse/WOLips IDE
214		-
215		-{{/note}}
216		-
217	217	== WO Scala Example ==
218	218
219	219	The following example is an almost 100% Scala WO app. In reality it is a mixed Java/Scala app:
220	220	All the EO logic and WO components are in Scala.
221		-Only the Application class is Java.
	207	+Only the Application class remains Java.
222	222
223	223	It is based on the D2W Movies example.
224	224
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226	226
227	227	=== Setup ===
228	228
229		-1. [[Install the Scala eclipse IDE>>http://www.scala-lang.org/node/94]]
230		-1. Install and start the OpenBase OBMovies database.
	215	+1. [[Install the Scala eclipse IDE>>http://www.scala-ide.org/]]
231	231	1. Right-click on Application.java and run as a WOApplication (as usual).
232	232
233		-==== EO Templates ====
	218	+{{note}}
234	234
	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	+== EO Templates ==
	225	+
235	235	When you create your ##.eogen## file, be sure to make the following changes in the EOGenerator Editor:
236	236
237		-1. Point to the local [[Scala versions>>http://wiki.objectstyle.org/confluence/display/WOL/EOGenerator+Templates+and+Additions]] of the .eotemplate files for ##Entity## and ##//Entity//##
	228	+1. Point to the local [[Scala versions>>http://wiki.objectstyle.org/confluence/display/WOL/EOGenerator+Templates+and+Additions]] of the .eotemplate files for ##Entity## and ##Entity##
238	238	1. Change the File Names Extension to "scala"
239	239	1. In Destination Paths set the Superclass Package (e.g: base)
240	240	1. Uncheck Java under Options
...	...	@@ -245,11 +245,3 @@
245	245	1. Set ##scala.home## (the location Scala has been installed onto) in the project ##build.properties## file
246	246	1. [[Add the scalac task and properties>>Configuring Ant to Build Scala with WebObjects]] to the ant build.xml file
247	247	1. Run from the project directory: ##sudo ant clean install##
248		-
249		-== Caveats ==
250		-
251		-{{warning}}
252		-
253		-Currently mixed Scala and Java projects aren't supported by the Scala Eclipse IDE, though it is possible to do so providing your project is either mostly Java or mostly Scala.
254		-
255		-{{/warning}}