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
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 | 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
	9	+Here's a quick summary:
14	14
	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	+
15	15	Other notable features include:
16	16
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)]]
	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
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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39	39
40	40	== EOs in Scala ==
41	41
42		-=== Thread-Safe Shared Vars ===
	43	+=== Thread-Safe Shared Vars ===
43	43
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	+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.
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).
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
51	51	Java:
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61	61
62	62	{{code}}
63	63
64		-object Talent {
	63	+object Talent extends EOGenericRecord {
65	65	val ENTITY_NAME = "Talent"
66	66
67	67	{{/code}}
...	...	@@ -76,6 +76,8 @@
76	76
77	77	==== Compacted imports ====
78	78
	78	+Two lines in Java are compacted into one in Scala.
	79	+
79	79	In Java:
80	80
81	81	{{code value="java"}}
...	...	@@ -164,9 +164,9 @@
164	164
165	165	An example of accessing variables in WebObjects with the following languages:
166	166
167		-|= |= Objective-C |= Java |= Scala
168		-|= getter | ##object name## | ##object.name()## | ##object.name##
169		-|= setter | ##object setName:aName## | ##object.setName(aName)## | ##object.name = aName##
	168	+|= |= Objective-C |= Java |= Scala
	169	+|= getter | ##object name## | ##object.name()## | ##object.name##
	170	+|= setter | ##object setName:aName## | ##object.setName(aName)## | ##object.name = aName##
170	170
171	171	Of course in Java, we may generate WebObjects classes with "get" methods as well in order to stick to convention.
172	172	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.
...	...	@@ -186,25 +186,38 @@
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:
	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.
190	190
191		-{{code value="java"}}
	193	+But one may modify the EO templates to produce API such as:
192	192
193		-import scala.collection.JavaConversions._
	195	+{{code}}
194	194
	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	+
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.
	207	+== How to Add Scala to a WO Project ==
198	198
199		-== How to Add Scala to a WO Project (in Eclipse) ==
200		-
201	201	{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
202	202
	211	+{{note}}
	212	+
	213	+This is for Eclipse/WOLips IDE
	214	+
	215	+{{/note}}
	216	+
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.
	221	+Only the Application class is Java.
208	208
209	209	It is based on the D2W Movies example.
210	210
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212	212
213	213	=== Setup ===
214	214
215		-1. [[Install the Scala eclipse IDE>>http://www.scala-ide.org/]]
	229	+1. [[Install the Scala eclipse IDE>>http://www.scala-lang.org/node/94]]
	230	+1. Install and start the OpenBase OBMovies database.
216	216	1. Right-click on Application.java and run as a WOApplication (as usual).
217	217
218		-{{note}}
	233	+==== EO Templates ====
219	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		-== EO Templates ==
225		-
226	226	When you create your ##.eogen## file, be sure to make the following changes in the EOGenerator Editor:
227	227
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##
	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//##
229	229	1. Change the File Names Extension to "scala"
230	230	1. In Destination Paths set the Superclass Package (e.g: base)
231	231	1. Uncheck Java under Options
...	...	@@ -236,3 +236,11 @@
236	236	1. Set ##scala.home## (the location Scala has been installed onto) in the project ##build.properties## file
237	237	1. [[Add the scalac task and properties>>Configuring Ant to Build Scala with WebObjects]] to the ant build.xml file
238	238	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}}