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 is a modern language not unlike Groovy.
	4	+It is said to be more powerful (and faster) than Groovy or Ruby which has been the reason for its adoption at sites like Twitter.
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 its features and paradigms favor multi-threading and concurrency. Some of these may not be unfamiliar to Objective-C and WebObjects developers. Here's a summary:
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
	8	+|= |= Objective-C |= Java |= Scala
	9	+|= Mutable/Immuable Datatypes | Collections //e.g: NSArray/NSMutableArray// | No | Yes
	10	+|= Closures | Blocks (//Extension//) | No | Yes
	11	+|= Static variables | Yes | Yes | No
	12	+|= Static methods/functions | Yes | Yes | No
	13	+|= Concurrency | [[Grand Central Dispatch>>http://en.wikipedia.org/wiki/Grand_Central_Dispatch]] (//Extension//)| //Threads// |[[Actors>>http://en.wikipedia.org/wiki/Actor_model]]
	14	+|= |= Weakly Typed |=--Strongly Typed--|= Strongly Typed
14	14
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)]]
	18	+|= |= Objective-C |= Java |= Scala
	19	+|= Parametered methods | Yes //e.g: addObject: to~:// | No | Yes //e.g: add(object= ,to=)//
	20	+|= Class composition | Categories | Interfaces | Traits
20	20
	22	+A fuller description of Scala can be found [[here>>http://en.wikipedia.org/wiki/Scala_(programming_language)]].
	23	+
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).
	26	+With Web 2.0, building concurrent WebObjects applications is a must.
	27	+Developing and maintaining a concurrent or multi-threaded WebObjects application can be challenging.
24	24
25		-=== Can WebObjects be Programmed In Scala? ===
	29	+Scala offers concurrency that is (effectively) built-in to the language and is inherently thread-safe.
26	26
27		-Yes. It is very simple.
28		-By virtue of being a JVM-language, Scala compiles to java bytecode.
	31	+In other words, developing Ajax (i.e asynchronous communication) with WO will require concurrent request handling and thread-safe code, for which Scala is a better choice than Java.
29	29
30		-Furthermore, being a multi-paradigm language grants Scala easy WebObjects-interoperability.
	33	+In addition it may offer new solutions for concurrency in WebObjects and EOF.
31	31
32		-===== Caveats =====
	35	+=== Can WebObjects be Programmed In Scala? ===
33	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.
	37	+Yes. It is very simple.
	38	+Scala compiles to java bytecode. Hence using it with WebObjects is fairly straightforward.
35	35
36	36	= WebObjects In Scala =
37	37
...	...	@@ -39,46 +39,36 @@
39	39
40	40	== EOs in Scala ==
41	41
42		-=== Thread-Safe Shared Vars ===
	46	+=== 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.
	48	+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.
	49	+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).
	51	+In Java:
48	48
49		-The following is an example of the use of a //Companion Object// for Talent in Scala instead of Talent static fields in Java.
	53	+{{code}}
50	50
51		-Java:
52		-
53		-{{code value="java"}}
54		-
55	55	public class _Talent extends EOGenericRecord {
56	56	public static final String ENTITY_NAME = "Talent";
57	57
58	58	{{/code}}
59	59
60		-Scala:
	60	+In Scala:
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}}
68	68
69		-This value will be accessed exactly the same way in both languages:
70		-
71		-{{code}}
72		-
73		-Talent.ENTITY_NAME
74		-
75		-{{/code}}
76		-
77	77	==== Compacted imports ====
78	78
	71	+Two lines in Java are compacted into one in Scala.
	72	+
79	79	In Java:
80	80
81		-{{code value="java"}}
	75	+{{code}}
82	82
83	83	import com.webobjects.eocontrol.EOGenericRecord;
84	84	import com.webobjects.eocontrol.EORelationshipManipulation;
...	...	@@ -101,7 +101,7 @@
101	101
102	102	In Java:
103	103
104		-{{code value="java"}}
	98	+{{code}}
105	105
106	106	public class MenuHeader extends WOComponent {
107	107
...	...	@@ -122,11 +122,11 @@
122	122	==== Simplified Exception Handling ====
123	123
124	124	Scala doesn't force you to catch exceptions unlike in Java.
125		-In addition, the syntax employs Scala's very powerful **pattern matching** to handle exceptions.
	119	+In addition, the syntax employs Scala's very powerful pattern matching to handle different exceptions.
126	126
127	127	In Java:
128	128
129		-{{code value="java"}}
	123	+{{code}}
130	130
131	131	try {
132	132	EditPageInterface epi = D2W.factory().editPageForNewObjectWithEntityNamed(_manipulatedEntityName, session());
...	...	@@ -160,79 +160,35 @@
160	160
161	161	{{/code}}
162	162
163		-==== Scala Annotations vs. Generated Accessors ====
	157	+== How to Add Scala to a WO Project ==
164	164
165		-An example of accessing variables in WebObjects with the following languages:
	159	+{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
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##
	161	+{{note title="Note"}}
170	170
171		-Of course in Java, we may generate WebObjects classes with "get" methods as well in order to stick to convention.
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.
	163	+This is for Eclipse/WOLips IDE
173	173
174		-E.g, in Main.scala we annotate our component keys with ##@BeanProperty## to automatically create public "set" and "get" methods.
175		-These variables can then be accessed via //KVC//.
	165	+{{/note}}
176	176
177		-{{code}}
178		-
179		-import scala.reflect.BeanProperty
180		-
181		-@BeanProperty var username = new String()
182		-@BeanProperty var password = new String()
183		-@BeanProperty var isAssistantCheckboxVisible = false
184		-
185		-{{/code}}
186		-
187		-== How to Use Scala Collections with EOF ==
188		-
189		-To use the Scala Collections API with an NSArray or NSDictionary you simply need to add an import:
190		-
191		-{{code value="java"}}
192		-
193		-import scala.collection.JavaConversions._
194		-
195		-{{/code}}
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.
198		-
199		-== How to Add Scala to a WO Project (in Eclipse) ==
200		-
201		-{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
202		-
203	203	== WO Scala Example ==
204	204
205		-The following example is an almost 100% Scala WO app. In reality it is a mixed Java/Scala app:
	169	+The following example is a mixed Java/Scala version of the WO Movies D2W app.
206	206	All the EO logic and WO components are in Scala.
207		-Only the Application class remains Java.
	171	+Only the Application class is Java.
208	208
209		-It is based on the D2W Movies example.
210		-
211	211	{{attachments patterns=".*zip"}}{{/attachments}}
212	212
213	213	=== Setup ===
214	214
215		-1. [[Install the Scala eclipse IDE>>http://www.scala-ide.org/]]
	177	+1. [[Install the Scala eclipse IDE>>http://www.scala-lang.org/node/94]]
	178	+1. Install and run the OpenBase OBMovies database.
216	216	1. Right-click on Application.java and run as a WOApplication (as usual).
217	217
218		-{{note}}
	181	+==== 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.
	183	+See: [[Scala templates>>http://wiki.objectstyle.org/confluence/display/WOL/EOGenerator+Templates+and+Additions]]
221	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##
229	229	1. Change the File Names Extension to "scala"
230		-1. In Destination Paths set the Superclass Package (e.g: base)
231	231	1. Uncheck Java under Options
232		-
233		-== How to Build & Deploy a WebObjects Scala Project with Ant ==
234		-
235		-1. [[Download>>http://www.scala-lang.org/downloads]] and install Scala
236		-1. Set ##scala.home## (the location Scala has been installed onto) in the project ##build.properties## file
237		-1. [[Add the scalac task and properties>>Configuring Ant to Build Scala with WebObjects]] to the ant build.xml file
238		-1. Run from the project directory: ##sudo ant clean install##