Changes for page WebObjects with Scala

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1	1	=== What is Scala? ===
2	2
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.
	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.
5	5
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	+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.
7	7
8		-|= |= Objective-C |= Java |= Scala
9		-|= Mutable/Immuable Datatypes | Collections //e.g: NSArray/NSMutableArray// | No | Yes
10		-|= Closures | Blocks (//Extension//) | No | Anonymous Functions
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
	9	+Here's a quick summary:
15	15
	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	+
16	16	Other notable features include:
17	17
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
	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
21	21
22		-A fuller description of Scala can be found [[here>>http://en.wikipedia.org/wiki/Scala_(programming_language)]].
23		-
24	24	=== Why Use Scala? ===
25	25
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.
	27	+Scala is inherently thread-safe.
	28	+It has concurrency that is effectively built-in to the language.
28	28
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.
	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).
31	31
32		-In addition it may offer new solutions for concurrency in WebObjects and EOF.
33		-
34	34	=== Can WebObjects be Programmed In Scala? ===
35	35
36	36	Yes. It is very simple.
...	...	@@ -47,20 +47,22 @@
47	47	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.
48	48	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.
49	49
50		-In Java:
	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	51
52		-{{code}}
	50	+Java:
53	53
	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		-In Scala:
	59	+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}}
	74	+{{code value="java"}}
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}}
	97	+{{code value="java"}}
98	98
99	99	public class MenuHeader extends WOComponent {
100	100
...	...	@@ -115,11 +115,11 @@
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 different exceptions.
	118	+In addition, the syntax employs Scala's very powerful **pattern matching** to handle exceptions.
119	119
120	120	In Java:
121	121
122		-{{code}}
	122	+{{code value="java"}}
123	123
124	124	try {
125	125	EditPageInterface epi = D2W.factory().editPageForNewObjectWithEntityNamed(_manipulatedEntityName, session());
...	...	@@ -153,9 +153,33 @@
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	+
156	156	== How to Use Scala Collections with EOF ==
157	157
158		-One of the benefits of Scala is its very powerful, concurrency-ready collection classes - primarily ##List##, ##Map##, ##Seq## and ##Set##.
	182	+One of the benefits of Scala is its very powerful, concurrency-ready collection classes - primarily ##List##, ##Map## and ##Set##.
159	159	Employing these instead of ##NSArray## and ##NSDictionary## in WebObjects/EOF may be challenging.
160	160
161	161	But one may modify the EO templates to produce API such as:
...	...	@@ -162,11 +162,11 @@
162	162
163	163	{{code}}
164	164
165		-def movies: NSArray[EOGenericRecord] = {
166		- storedValueForKey(_Studio.Keys.MOVIES).asInstanceOf[NSArray[EOGenericRecord]]
	189	+def movies: NSArray[Studio] = {
	190	+ storedValueForKey(_Studio.Keys.MOVIES).asInstanceOf[NSArray[Studio]]
167	167	}
168	168
169		-def moviesList: List[EOGenericRecord] = {
	193	+def moviesList: List[Studio] = {
170	170	movies.objects.toList
171	171	}
172	172
...	...	@@ -176,7 +176,7 @@
176	176
177	177	{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
178	178
179		-{{note title="Note"}}
	203	+{{note}}
180	180
181	181	This is for Eclipse/WOLips IDE
182	182
...	...	@@ -195,15 +195,29 @@
195	195	=== Setup ===
196	196
197	197	1. [[Install the Scala eclipse IDE>>http://www.scala-lang.org/node/94]]
198		-1. Install and run the OpenBase OBMovies database.
	222	+1. Install and start the OpenBase OBMovies database.
199	199	1. Right-click on Application.java and run as a WOApplication (as usual).
200	200
201	201	==== EO Templates ====
202	202
203		-See: [[Scala templates>>http://wiki.objectstyle.org/confluence/display/WOL/EOGenerator+Templates+and+Additions]]
204		-
205	205	When you create your ##.eogen## file, be sure to make the following changes in the EOGenerator Editor:
206	206
207		-1. Point to the local .eotemplate files for ##Entity## and ##//Entity//##
	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//##
208	208	1. Change the File Names Extension to "scala"
	231	+1. In Destination Paths set the Superclass Package (e.g: base)
209	209	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##
	240	+
	241	+== Caveats ==
	242	+
	243	+{{warning}}
	244	+
	245	+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.
	246	+
	247	+{{/warning}}