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:
10		-
11	11	|= |= Objective-C |= Java |= Scala
12	12	|= Mutable/Immuable Datatypes | Collections //e.g: NSArray/NSMutableArray// | No | Yes
13	13	|= Closures | Blocks (//Extension//) | No | Anonymous Functions
14	14	|= Static variables | Yes | Yes | No
15		-|= Static methods or functions| Yes | Yes | No
	12	+|= Static methods/functions | Yes | Yes | No
16	16	|= Concurrency | [[Grand Central Dispatch>>http://en.wikipedia.org/wiki/Grand_Central_Dispatch]] (//Extension//)| //Threads// |[[Actors>>http://en.wikipedia.org/wiki/Actor_model]]
17	17	|= |= Weakly Typed |=--Strongly Typed--|= Strongly Typed
18	18
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22	22	|= Parametered methods | Yes //e.g: addObject: to~:// | No | Yes //e.g: add(object= ,to=)//
23	23	|= 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.
	30	+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.
31	31
	32	+In addition it may offer new solutions for concurrency in WebObjects and EOF.
	33	+
32	32	=== Can WebObjects be Programmed In Scala? ===
33	33
34	34	Yes. It is very simple.
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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.
	50	+In Java:
49	49
50		-Java:
	52	+{{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:
	59	+In Scala:
60	60
61	61	{{code}}
62	62
63		-object Talent extends EOGenericRecord {
	63	+object _Talent extends EOGenericRecord {
64	64	val ENTITY_NAME = "Talent"
65	65
66	66	{{/code}}
...	...	@@ -71,7 +71,7 @@
71	71
72	72	In Java:
73	73
74		-{{code value="java"}}
	74	+{{code}}
75	75
76	76	import com.webobjects.eocontrol.EOGenericRecord;
77	77	import com.webobjects.eocontrol.EORelationshipManipulation;
...	...	@@ -94,7 +94,7 @@
94	94
95	95	In Java:
96	96
97		-{{code value="java"}}
	97	+{{code}}
98	98
99	99	public class MenuHeader extends WOComponent {
100	100
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115	115	==== Simplified Exception Handling ====
116	116
117	117	Scala doesn't force you to catch exceptions unlike in Java.
118		-In addition, the syntax employs Scala's very powerful **pattern matching** to handle exceptions.
	118	+In addition, the syntax employs Scala's very powerful pattern matching to handle different exceptions.
119	119
120	120	In Java:
121	121
122		-{{code value="java"}}
	122	+{{code}}
123	123
124	124	try {
125	125	EditPageInterface epi = D2W.factory().editPageForNewObjectWithEntityNamed(_manipulatedEntityName, session());
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153	153
154	154	{{/code}}
155	155
156		-==== Scala Annotations vs. Generated Accessors ====
157		-
158		-An example of accessing variables in WebObjects with the following languages:
159		-
160		-|= |= Objective-C |= Java |= Scala
161		-|= getter | ##object name## | ##object.name()## | ##object.name##
162		-|= setter | ##object setName:aName## | ##object.setName(aName)## | ##object.name = aName##
163		-
164		-Of course in Java, we may generate WebObjects classes with "get" methods as well in order to stick to convention.
165		-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.
166		-
167		-E.g, in Main.scala we annotate our component keys with ##@BeanProperty## to automatically create public "set" and "get" methods.
168		-These variables can then be accessed via //KVC//.
169		-
170		-{{code}}
171		-
172		-import scala.reflect.BeanProperty
173		-
174		-@BeanProperty var username = new String()
175		-@BeanProperty var password = new String()
176		-@BeanProperty var isAssistantCheckboxVisible = false
177		-
178		-{{/code}}
179		-
180	180	== How to Use Scala Collections with EOF ==
181	181
182		-One of the benefits of Scala is its very powerful, concurrency-ready collection classes - primarily ##List##, ##Map## and ##Set##.
	158	+One of the benefits of Scala is its very powerful, concurrency-ready collection classes - primarily ##List##, ##Map##, ##Seq## and ##Set##.
183	183	Employing these instead of ##NSArray## and ##NSDictionary## in WebObjects/EOF may be challenging.
184	184
185	185	But one may modify the EO templates to produce API such as:
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219	219	=== Setup ===
220	220
221	221	1. [[Install the Scala eclipse IDE>>http://www.scala-lang.org/node/94]]
222		-1. Install and start the OpenBase OBMovies database.
	198	+1. Install and run the OpenBase OBMovies database.
223	223	1. Right-click on Application.java and run as a WOApplication (as usual).
224	224
225	225	==== EO Templates ====
226	226
	203	+See: [[Scala templates>>http://wiki.objectstyle.org/confluence/display/WOL/EOGenerator+Templates+and+Additions]]
	204	+
227	227	When you create your ##.eogen## file, be sure to make the following changes in the EOGenerator Editor:
228	228
229		-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//##
	207	+1. Point to the local .eotemplate files for ##Entity## and ##//Entity//##
230	230	1. Change the File Names Extension to "scala"
231		-1. In Destination Paths set the Superclass Package (e.g: base)
232	232	1. Uncheck Java under Options
233		-
234		-== How to Build & Deploy a WebObjects Scala Project with Ant ==
235		-
236		-1. [[Download>>http://www.scala-lang.org/downloads]] and install Scala
237		-1. Set ##scala.home## (the location Scala has been installed onto) in the project ##build.properties## file
238		-1. [[Add the scalac task and properties>>Configuring Ant to Build Scala with WebObjects]] to the ant build.xml file
239		-1. Run from the project directory: ##sudo ant clean install##