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
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	+|= 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. (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:
...	...	@@ -52,9 +52,8 @@
52	52
53	53	{{code value="java"}}
54	54
55		-public class Talent extends EOGenericRecord {
	54	+public class _Talent extends EOGenericRecord {
56	56	public static final String ENTITY_NAME = "Talent";
57		-}
58	58
59	59	{{/code}}
60	60
...	...	@@ -62,22 +62,15 @@
62	62
63	63	{{code}}
64	64
65		-object Talent {
	63	+object Talent extends EOGenericRecord {
66	66	val ENTITY_NAME = "Talent"
67		-}
68	68
69	69	{{/code}}
70	70
71		-This value will be accessed exactly the same way in both languages:
72		-
73		-{{code}}
74		-
75		-Talent.ENTITY_NAME
76		-
77		-{{/code}}
78		-
79	79	==== Compacted imports ====
80	80
	70	+Two lines in Java are compacted into one in Scala.
	71	+
81	81	In Java:
82	82
83	83	{{code value="java"}}
...	...	@@ -110,7 +110,6 @@
110	110	public MenuHeader(WOContext aContext) {
111	111	super(aContext);
112	112	}
113		-}
114	114
115	115	{{/code}}
116	116
...	...	@@ -163,13 +163,13 @@
163	163
164	164	{{/code}}
165	165
166		-==== Scala Annotations vs. Generated Accessors ====
	156	+==== Scala Annotations vs. Generic Accessors ====
167	167
168		-Here's an example of accessing variables in the following languages:
	158	+An example of accessing variables in WebObjects with the following languages:
169	169
170		-|= |= Objective-C |= Java |= Scala
171		-|= getter | ##object name## | ##object.name()## | ##object.name##
172		-|= setter | ##object setName:aName## | ##object.setName(aName)## | ##object.name = aName##
	160	+|= |= Objective-C |= Java |= Scala
	161	+|= getter | ##object name## | ##object.name()## | ##object.name##
	162	+|= setter | ##object setName:aName## | ##object.setName(aName)## | ##object.name = aName##
173	173
174	174	Of course in Java, we may generate WebObjects classes with "get" methods as well in order to stick to convention.
175	175	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.
...	...	@@ -179,8 +179,6 @@
179	179
180	180	{{code}}
181	181
182		-import scala.reflect.BeanProperty
183		-
184	184	@BeanProperty var username = new String()
185	185	@BeanProperty var password = new String()
186	186	@BeanProperty var isAssistantCheckboxVisible = false
...	...	@@ -189,25 +189,38 @@
189	189
190	190	== How to Use Scala Collections with EOF ==
191	191
192		-To use the Scala Collections API with an NSArray or NSDictionary you simply need to add an import:
	180	+One of the benefits of Scala is its very powerful, concurrency-ready collection classes - primarily ##List##, ##Map##, ##Seq## and ##Set##.
	181	+Employing these instead of ##NSArray## and ##NSDictionary## in WebObjects/EOF may be challenging.
193	193
194		-{{code value="java"}}
	183	+But one may modify the EO templates to produce API such as:
195	195
196		-import scala.collection.JavaConversions._
	185	+{{code}}
197	197
	187	+def movies: NSArray[EOGenericRecord] = {
	188	+ storedValueForKey(_Studio.Keys.MOVIES).asInstanceOf[NSArray[EOGenericRecord]]
	189	+}
	190	+
	191	+def moviesList: List[EOGenericRecord] = {
	192	+ movies.objects.toList
	193	+}
	194	+
198	198	{{/code}}
199	199
200		-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.
	197	+== How to Add Scala to a WO Project ==
201	201
202		-== How to Add Scala to a WO Project (in Eclipse) ==
203		-
204	204	{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
205	205
	201	+{{note title="Note"}}
	202	+
	203	+This is for Eclipse/WOLips IDE
	204	+
	205	+{{/note}}
	206	+
206	206	== WO Scala Example ==
207	207
208	208	The following example is an almost 100% Scala WO app. In reality it is a mixed Java/Scala app:
209	209	All the EO logic and WO components are in Scala.
210		-Only the Application class remains Java.
	211	+Only the Application class is Java.
211	211
212	212	It is based on the D2W Movies example.
213	213
...	...	@@ -215,20 +215,15 @@
215	215
216	216	=== Setup ===
217	217
218		-1. [[Install the Scala eclipse IDE>>http://download.scala-ide.org/]]
	219	+1. [[Install the Scala eclipse IDE>>http://www.scala-lang.org/node/94]]
	220	+1. Install and start the OpenBase OBMovies database.
219	219	1. Right-click on Application.java and run as a WOApplication (as usual).
220	220
221		-{{note}}
	223	+==== EO Templates ====
222	222
223		-Application can be made into a Scala class as well, but then you will have to create a launcher in Eclipse manually.
224		-
225		-{{/note}}
226		-
227		-== EO Templates ==
228		-
229	229	When you create your ##.eogen## file, be sure to make the following changes in the EOGenerator Editor:
230	230
231		-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##
	227	+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//##
232	232	1. Change the File Names Extension to "scala"
233	233	1. In Destination Paths set the Superclass Package (e.g: base)
234	234	1. Uncheck Java under Options