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.
...	...	@@ -45,34 +45,24 @@
45	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	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.
47	47
48		-The following is an example of the use of a //Companion Object// for Talent in Scala instead of Talent static fields in Java.
	51	+In Java:
49	49
50		-Java:
	53	+{{code}}
51	51
52		-{{code value="java"}}
53		-
54	54	public class _Talent extends EOGenericRecord {
55	55	public static final String ENTITY_NAME = "Talent";
56	56
57	57	{{/code}}
58	58
59		-Scala:
	60	+In Scala:
60	60
61	61	{{code}}
62	62
63		-object Talent extends EOGenericRecord {
	64	+object _Talent extends EOGenericRecord {
64	64	val ENTITY_NAME = "Talent"
65	65
66	66	{{/code}}
67	67
68		-This value will be accessed exactly the same way in both languages:
69		-
70		-{{code}}
71		-
72		-Talent.ENTITY_NAME
73		-
74		-{{/code}}
75		-
76	76	==== Compacted imports ====
77	77
78	78	Two lines in Java are compacted into one in Scala.
...	...	@@ -79,7 +79,7 @@
79	79
80	80	In Java:
81	81
82		-{{code value="java"}}
	75	+{{code}}
83	83
84	84	import com.webobjects.eocontrol.EOGenericRecord;
85	85	import com.webobjects.eocontrol.EORelationshipManipulation;
...	...	@@ -102,7 +102,7 @@
102	102
103	103	In Java:
104	104
105		-{{code value="java"}}
	98	+{{code}}
106	106
107	107	public class MenuHeader extends WOComponent {
108	108
...	...	@@ -123,11 +123,11 @@
123	123	==== Simplified Exception Handling ====
124	124
125	125	Scala doesn't force you to catch exceptions unlike in Java.
126		-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.
127	127
128	128	In Java:
129	129
130		-{{code value="java"}}
	123	+{{code}}
131	131
132	132	try {
133	133	EditPageInterface epi = D2W.factory().editPageForNewObjectWithEntityNamed(_manipulatedEntityName, session());
...	...	@@ -161,54 +161,11 @@
161	161
162	162	{{/code}}
163	163
164		-==== Scala Annotations vs. Generated Accessors ====
165		-
166		-An example of accessing variables in WebObjects with the following languages:
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##
171		-
172		-Of course in Java, we may generate WebObjects classes with "get" methods as well in order to stick to convention.
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.
174		-
175		-E.g, in Main.scala we annotate our component keys with ##@BeanProperty## to automatically create public "set" and "get" methods.
176		-These variables can then be accessed via //KVC//.
177		-
178		-{{code}}
179		-
180		-import scala.reflect.BeanProperty
181		-
182		-@BeanProperty var username = new String()
183		-@BeanProperty var password = new String()
184		-@BeanProperty var isAssistantCheckboxVisible = false
185		-
186		-{{/code}}
187		-
188		-== How to Use Scala Collections with EOF ==
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.
192		-
193		-But one may modify the EO templates to produce API such as:
194		-
195		-{{code}}
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		-{{/code}}
206		-
207	207	== How to Add Scala to a WO Project ==
208	208
209	209	{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
210	210
211		-{{note}}
	161	+{{note title="Note"}}
212	212
213	213	This is for Eclipse/WOLips IDE
214	214
...	...	@@ -216,40 +216,23 @@
216	216
217	217	== WO Scala Example ==
218	218
219		-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.
220	220	All the EO logic and WO components are in Scala.
221	221	Only the Application class is Java.
222	222
223		-It is based on the D2W Movies example.
224		-
225	225	{{attachments patterns=".*zip"}}{{/attachments}}
226	226
227	227	=== Setup ===
228	228
229	229	1. [[Install the Scala eclipse IDE>>http://www.scala-lang.org/node/94]]
230		-1. Install and start the OpenBase OBMovies database.
	178	+1. Install and run the OpenBase OBMovies database.
231	231	1. Right-click on Application.java and run as a WOApplication (as usual).
232	232
233	233	==== EO Templates ====
234	234
	183	+See: [[Scala templates>>http://wiki.objectstyle.org/confluence/display/WOL/EOGenerator+Templates+and+Additions]]
	184	+
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//##
238	238	1. Change the File Names Extension to "scala"
239		-1. In Destination Paths set the Superclass Package (e.g: base)
240	240	1. Uncheck Java under Options
241		-
242		-== How to Build & Deploy a WebObjects Scala Project with Ant ==
243		-
244		-1. [[Download>>http://www.scala-lang.org/downloads]] and install Scala
245		-1. Set ##scala.home## (the location Scala has been installed onto) in the project ##build.properties## file
246		-1. [[Add the scalac task and properties>>Configuring Ant to Build Scala with WebObjects]] to the ant build.xml file
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}}