Changes for page WebObjects with Scala

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1	1	=== What is Scala? ===
2		-
3		-Scala is a modern language not unlike Groovy.
4		-It is said to be more powerful (and faster) than Groovy or Rails which has been the reason for its adoption at sites like Twitter.
5		-
6		-Many of its features and paradigms favor multi-threaded and concurrent development which may not be unfamiliar to Objective-C and WebObjects developers. Here's a summary:
7		-
8		-|= |= Objective-C |= Java |= Scala
9		-|= Mutable/Immuable Datatypes | Collections //e.g: NSArray/NSMutableArray// | No | //All datatypes//
10		-|= Closures | Blocks (//Extension//) | No | //Built-in//
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
15		-
16		-Other notable features include:
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		-
22		-A fuller description of Scala can be found [[here>>http://en.wikipedia.org/wiki/Scala_(programming_language)]].
23		-
24		-=== Why Use Scala? ===
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.
28		-
29		-Scala offers concurrency that is (effectively) built-in to the language and is inherently thread-safe.
30		-So it may offer new solutions for concurrency in WebObjects.
31		-
32		-=== Can WebObjects be Programmed In Scala? ===
33		-
34		-Yes. It is very simple.
35		-Scala compiles to java bytecode. Hence using it with WebObjects is fairly straightforward.
36		-
37		-= WebObjects In Scala =
38		-
39		-The following is an in-depth explanation of differences between Java and Scala in WebObjects:
40		-
41		-== EOs in Scala ==
42		-
43		-=== Thread-Safe Shared Constants and Vars ===
44		-
45		-Scala doesn't have static variables or methods. However, every class does have a //Companion Object// that will allow you to achieve something equivalent to static variables.
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		-
48		-In Java:
49		-
50		-{{code}}
51		-
52		-public class _Talent extends EOGenericRecord {
53		- public static final String ENTITY_NAME = "Talent";
54		-
55		-{{/code}}
56		-
57		-In Scala:
58		-
59		-{{code}}
60		-
61		-object _Talent extends EOGenericRecord {
62		- val ENTITY_NAME = "Talent"
63		-
64		-{{/code}}
65		-
66		-==== Compacted imports ====
67		-
68		-Two lines in Java is compacted into one in Scala.
69		-
70		-In Java:
71		-
72		-{{code}}
73		-
74		-import com.webobjects.eocontrol.EOGenericRecord;
75		-import com.webobjects.eocontrol.EORelationshipManipulation;
76		-
77		-{{/code}}
78		-
79		-In Scala:
80		-
81		-{{code}}
82		-
83		-import com.webobjects.eocontrol.{EOGenericRecord, EORelationshipManipulation}
84		-
85		-{{/code}}
86		-
87		-== WOComponents in Scala ==
88		-
89		-==== Compact Constructors ====
90		-
91		-Scala allows for simpler use of multi-valued constructors than Java.
92		-
93		-In Java:
94		-
95		-{{code}}
96		-
97		-public class MenuHeader extends WOComponent {
98		-
99		- public MenuHeader(WOContext aContext) {
100		- super(aContext);
101		- }
102		-
103		-{{/code}}
104		-
105		-In Scala:
106		-
107		-{{code}}
108		-
109		-class MenuHeader(context: WOContext) extends WOComponent(context: WOContext) {
110		-
111		-{{/code}}
112		-
113		-==== Simplified Exception Handling ====
114		-
115		-Scala doesn't force you to catch exceptions unlike in Java.
116		-In addition, the syntax employs Scala's very powerful pattern matching to handle different exceptions.
117		-
118		-In Java:
119		-
120		-{{code}}
121		-
122		-try {
123		- EditPageInterface epi = D2W.factory().editPageForNewObjectWithEntityNamed(_manipulatedEntityName, session());
124		- epi.setNextPage(context().page());
125		- nextPage = (WOComponent) epi;
126		-} catch (IllegalArgumentException e) {
127		- ErrorPageInterface epf = D2W.factory().errorPage(session());
128		- epf.setMessage(e.toString());
129		- epf.setNextPage(context().page());
130		- nextPage = (WOComponent) epf;
131		-}
132		-
133		-{{/code}}
134		-
135		-In Scala:
136		-
137		-{{code}}
138		-
139		-try {
140		- var epi: EditPageInterface = D2W.factory.editPageForNewObjectWithEntityNamed(_manipulatedEntityName, session)
141		- epi.setNextPage(context.page)
142		- nextPage = epi.asInstanceOf[WOComponent]
143		-} catch {
144		- case e: IllegalArgumentException => {
145		- var epf: ErrorPageInterface = D2W.factory.errorPage(session)
146		- epf.setMessage(e.toString)
147		- epf.setNextPage(context.page)
148		- nextPage = epf.asInstanceOf[WOComponent]
149		- }
150		-}
151		-
152		-{{/code}}
153		-
154		-== How to Add Scala to a WO Project ==
155		-
156		-{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
157		-
158		-{{note title="Note"}}
159		-
160		-This is for Eclipse/WOLips IDE
161		-
162		-{{/note}}
163		-
164		-== WO Scala Example ==
165		-
166		-The following is a mixed Java/Scala version of the WO Movies D2W app.
167		-All the EO logic and WO components are in Scala.
168		-Only the Application class is Java.
169		-
170		-{{attachments patterns=".*zip"}}{{/attachments}}
171		-
172		-=== Setup ===
173		-
174		-1. Install and run the OpenBase OBMovies database.
175		-1. Right-click on Application.java and run as a WOApplication (as usual).
176		-
177		-==== EO Templates ====
178		-
179		-See: [[Scala templates>>http://wiki.objectstyle.org/confluence/display/WOL/EOGenerator+Templates+and+Additions]]
180		-
181		-When you create your ##.eogen## file, be sure to make the following changes in the EOGenerator Editor:
182		-
183		-1. Change the File Names Extension to "scala"
184		-1. Uncheck Java under Options