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 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.
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.
	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:
8	8
9		-Here's a quick summary:
	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
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
	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
24	24
	22	+A fuller description of Scala can be found [[here>>http://en.wikipedia.org/wiki/Scala_(programming_language)]].
	23	+
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.
	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.
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).
	29	+Scala offers concurrency that is (effectively) built-in to the language and is inherently thread-safe.
31	31
	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.
	32	+
	33	+In addition it may offer new solutions for concurrency in WebObjects and EOF.
	34	+
32	32	=== Can WebObjects be Programmed In Scala? ===
33	33
34	34	Yes. It is very simple.
...	...	@@ -40,40 +40,29 @@
40	40
41	41	== EOs in Scala ==
42	42
43		-=== Thread-Safe Shared Vars ===
	46	+=== Thread-Safe Shared Vars ===
44	44
45		-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.
46	46
47		-So you don't have to worry about synchronizing access to shared mutable fields in a concurrent application.
	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 extends EOGenericRecord {
	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
79	79	Two lines in Java are compacted into one in Scala.
...	...	@@ -80,7 +80,7 @@
80	80
81	81	In Java:
82	82
83		-{{code value="java"}}
	75	+{{code}}
84	84
85	85	import com.webobjects.eocontrol.EOGenericRecord;
86	86	import com.webobjects.eocontrol.EORelationshipManipulation;
...	...	@@ -103,7 +103,7 @@
103	103
104	104	In Java:
105	105
106		-{{code value="java"}}
	98	+{{code}}
107	107
108	108	public class MenuHeader extends WOComponent {
109	109
...	...	@@ -124,11 +124,11 @@
124	124	==== Simplified Exception Handling ====
125	125
126	126	Scala doesn't force you to catch exceptions unlike in Java.
127		-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.
128	128
129	129	In Java:
130	130
131		-{{code value="java"}}
	123	+{{code}}
132	132
133	133	try {
134	134	EditPageInterface epi = D2W.factory().editPageForNewObjectWithEntityNamed(_manipulatedEntityName, session());
...	...	@@ -162,58 +162,11 @@
162	162
163	163	{{/code}}
164	164
165		-==== Scala Annotations vs. Generated Accessors ====
166		-
167		-An example of accessing variables in WebObjects with the following languages:
168		-
169		-|= |= Objective-C |= Java |= Scala
170		-|= getter | ##object name## | ##object.name()## | ##object.name##
171		-|= setter | ##object setName:aName## | ##object.setName(aName)## | ##object.name = aName##
172		-
173		-Of course in Java, we may generate WebObjects classes with "get" methods as well in order to stick to convention.
174		-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.
175		-
176		-E.g, in Main.scala we annotate our component keys with ##@BeanProperty## to automatically create public "set" and "get" methods.
177		-These variables can then be accessed via //KVC//.
178		-
179		-{{code}}
180		-
181		-import scala.reflect.BeanProperty
182		-
183		-@BeanProperty var username = new String()
184		-@BeanProperty var password = new String()
185		-@BeanProperty var isAssistantCheckboxVisible = false
186		-
187		-{{/code}}
188		-
189		-== How to Use Scala Collections with EOF ==
190		-
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.
193		-
194		-But one may modify the EO templates to produce API such as:
195		-
196		-{{code}}
197		-
198		-import scala.collection.JavaConversions._
199		-
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		-
208		-{{/code}}
209		-
210		-This employs a feature of Scala known as **implicit conversions** to automagically convert a NSArray (a Java Iterable) into a Scala Iterable.
211		-
212	212	== How to Add Scala to a WO Project ==
213	213
214	214	{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
215	215
216		-{{note}}
	161	+{{note title="Note"}}
217	217
218	218	This is for Eclipse/WOLips IDE
219	219
...	...	@@ -221,31 +221,23 @@
221	221
222	222	== WO Scala Example ==
223	223
224		-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.
225	225	All the EO logic and WO components are in Scala.
226	226	Only the Application class is Java.
227	227
228		-It is based on the D2W Movies example.
229		-
230	230	{{attachments patterns=".*zip"}}{{/attachments}}
231	231
232	232	=== Setup ===
233	233
234		-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.
235	235	1. Right-click on Application.java and run as a WOApplication (as usual).
236	236
237		-== EO Templates ==
	181	+==== EO Templates ====
238	238
	183	+See: [[Scala templates>>http://wiki.objectstyle.org/confluence/display/WOL/EOGenerator+Templates+and+Additions]]
	184	+
239	239	When you create your ##.eogen## file, be sure to make the following changes in the EOGenerator Editor:
240	240
241		-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##
242	242	1. Change the File Names Extension to "scala"
243		-1. In Destination Paths set the Superclass Package (e.g: base)
244	244	1. Uncheck Java under Options
245		-
246		-== How to Build & Deploy a WebObjects Scala Project with Ant ==
247		-
248		-1. [[Download>>http://www.scala-lang.org/downloads]] and install Scala
249		-1. Set ##scala.home## (the location Scala has been installed onto) in the project ##build.properties## file
250		-1. [[Add the scalac task and properties>>Configuring Ant to Build Scala with WebObjects]] to the ant build.xml file
251		-1. Run from the project directory: ##sudo ant clean install##