Changes for page WebObjects with Scala

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1		-XWiki.johnthuss
	1	+XWiki.rmendis

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1	1	=== What is Scala? ===
2	2
3		-[[Scala>>http://en.wikipedia.org/wiki/Scala_(programming_language)]] is a JVM language that is a hybrid of Object-Oriented and Functional styles.  It is useful as complete general purpose replacement for Java.  But its built-in Actors library makes it especially attractive for concurrent computing.
	3	+Scala is a language for concurrent computing.
4	4	In this day and age of multi-core processors, concurrent computing can't be ignored.
5	5
6		-Many of Scala's features have been designed with concurrency in mind, primarily a preference for immutability and the use of other functional language paradigms.
	6	+Many of Scala's features have been designed with concurrency in mind.
7	7	Some of these may not be unfamiliar to Objective-C or WebObjects developers.
8	8
9	9	Here's a quick summary:
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
	11	+|= |= Objective-C |= Java |= Scala
	12	+|= 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	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
	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
24	24
	25	+A fuller description of Scala can be found [[here>>http://en.wikipedia.org/wiki/Scala_(programming_language)]].
	26	+
25	25	=== Why Use Scala? ===
26	26
27		-Scala can help you to write thread-safe code.
28		-It has concurrency that is built-in to the standard library, primarily via Actors.
	29	+Scala is inherently thread-safe.
	30	+It has concurrency that is effectively built-in to the language.
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).
	32	+So for WebObjects developers, Scala offers itself as a powerful, safe and easy-to-use solution for concurrent applications. (In other words, Scala Actors can be used for problems that would have normally required threads).
31	31
32	32	=== Can WebObjects be Programmed In Scala? ===
33	33
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40	40
41	41	== EOs in Scala ==
42	42
43		-=== Thread-Safe Shared Vars ===
	45	+=== 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. Is this true?  I don't think Scala "object" instances (with the object keyword) are guaranteed to be thread-safe; they are just singletons
	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	+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.
48		-
49	49	The following is an example of the use of a //Companion Object// for Talent in Scala instead of Talent static fields in Java.
50	50
51	51	Java:
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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.
...	...	@@ -162,13 +162,13 @@
162	162
163	163	{{/code}}
164	164
165		-==== Scala Annotations vs. Generated Accessors ====
	158	+==== Scala Annotations vs. Generic Accessors ====
166	166
167	167	An example of accessing variables in WebObjects with the following languages:
168	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##
	162	+|= |= Objective-C |= Java |= Scala
	163	+|= getter | ##object name## | ##object.name()## | ##object.name##
	164	+|= setter | ##object setName:aName## | ##object.setName(aName)## | ##object.name = aName##
172	172
173	173	Of course in Java, we may generate WebObjects classes with "get" methods as well in order to stick to convention.
174	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.
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178	178
179	179	{{code}}
180	180
181		-import scala.reflect.BeanProperty
182		-
183	183	@BeanProperty var username = new String()
184	184	@BeanProperty var password = new String()
185	185	@BeanProperty var isAssistantCheckboxVisible = false
...	...	@@ -188,15 +188,28 @@
188	188
189	189	== How to Use Scala Collections with EOF ==
190	190
191		-To use the Scala Collections API with an NSArray or NSDictionary you simply need to add an import:import scala.collection.JavaConversions.
	182	+One of the benefits of Scala is its very powerful, concurrency-ready collection classes - primarily ##List##, ##Map##, ##Seq## and ##Set##.
	183	+Employing these instead of ##NSArray## and ##NSDictionary## in WebObjects/EOF may be challenging.
192	192
193		-Then you can access the typical Scala collection methods directly on NSArray.  This employs a feature of Scala known as implicit conversions to automagically cast a NSArray (a Java Iterable) into a Scala Iterable while leaving the actual object unchanged.  Alternatively, you could generate an actual new scala.List instance by calling myNSArray.toList.
	185	+But one may modify the EO templates to produce API such as:
194	194
	187	+{{code}}
	188	+
	189	+def movies: NSArray[EOGenericRecord] = {
	190	+ storedValueForKey(_Studio.Keys.MOVIES).asInstanceOf[NSArray[EOGenericRecord]]
	191	+}
	192	+
	193	+def moviesList: List[EOGenericRecord] = {
	194	+ movies.objects.toList
	195	+}
	196	+
	197	+{{/code}}
	198	+
195	195	== How to Add Scala to a WO Project ==
196	196
197	197	{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
198	198
199		-{{note}}
	203	+{{note title="Note"}}
200	200
201	201	This is for Eclipse/WOLips IDE
202	202
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206	206
207	207	The following example is an almost 100% Scala WO app. In reality it is a mixed Java/Scala app:
208	208	All the EO logic and WO components are in Scala.
209		-Only the Application class remains Java.
	213	+Only the Application class is Java.
210	210
211	211	It is based on the D2W Movies example.
212	212
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214	214
215	215	=== Setup ===
216	216
217		-1. [[Install the Scala eclipse IDE>>http://www.scala-ide.org/]]
	221	+1. [[Install the Scala eclipse IDE>>http://www.scala-lang.org/node/94]]
	222	+1. Install and start the OpenBase OBMovies database.
218	218	1. Right-click on Application.java and run as a WOApplication (as usual).
219	219
220		-Application can be made into a Scala class as well, but then you will have to create a launcher in Eclipse manually.
	225	+==== EO Templates ====
221	221
222		-== EO Templates ==
223		-
224	224	When you create your ##.eogen## file, be sure to make the following changes in the EOGenerator Editor:
225	225
226		-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##
	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//##
227	227	1. Change the File Names Extension to "scala"
228	228	1. In Destination Paths set the Superclass Package (e.g: base)
229	229	1. Uncheck Java under Options