Changes for page WebObjects with Scala

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1		-XWiki.rmendis
	1	+XWiki.johnthuss

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1	1	=== What is Scala? ===
2	2
3		-Scala is a language for concurrent computing.
	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.
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.
	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.
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		-|= 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	+|= 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	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		-
27	27	=== Why Use Scala? ===
28	28
29		-Scala is inherently thread-safe.
30		-It has concurrency that is effectively built-in to the language.
	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.
31	31
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).
	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).
33	33
34	34	=== Can WebObjects be Programmed In Scala? ===
35	35
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42	42
43	43	== EOs in Scala ==
44	44
45		-=== Thread-Safe Shared Vars ===
	43	+=== Thread-Safe Shared Vars ===
46	46
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.
	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
49	49
	47	+So you don't have to worry about synchronizing access to shared mutable fields in a concurrent application.
	48	+
50	50	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	52	Java:
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67	67
68	68	{{/code}}
69	69
	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	+
70	70	==== Compacted imports ====
71	71
72	72	Two lines in Java are compacted into one in Scala.
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155	155
156	156	{{/code}}
157	157
158		-==== Scala Annotations vs. Generic Accessors ====
	165	+==== Scala Annotations vs. Generated Accessors ====
159	159
160	160	An example of accessing variables in WebObjects with the following languages:
161	161
162		-|= |= Objective-C |= Java |= Scala
163		-|= getter | ##object name## | ##object.name()## | ##object.name##
164		-|= setter | ##object setName:aName## | ##object.setName(aName)## | ##object.name = aName##
	169	+|= |= Objective-C |= Java |= Scala
	170	+|= getter | ##object name## | ##object.name()## | ##object.name##
	171	+|= setter | ##object setName:aName## | ##object.setName(aName)## | ##object.name = aName##
165	165
166	166	Of course in Java, we may generate WebObjects classes with "get" methods as well in order to stick to convention.
167	167	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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171	171
172	172	{{code}}
173	173
	181	+import scala.reflect.BeanProperty
	182	+
174	174	@BeanProperty var username = new String()
175	175	@BeanProperty var password = new String()
176	176	@BeanProperty var isAssistantCheckboxVisible = false
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179	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##, ##Seq## and ##Set##.
183		-Employing these instead of ##NSArray## and ##NSDictionary## in WebObjects/EOF may be challenging.
	191	+To use the Scala Collections API with an NSArray or NSDictionary you simply need to add an import:import scala.collection.JavaConversions.
184	184
185		-But one may modify the EO templates to produce API such as:
	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.
186	186
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		-
199	199	== How to Add Scala to a WO Project ==
200	200
201	201	{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
202	202
203		-{{note title="Note"}}
	199	+{{note}}
204	204
205	205	This is for Eclipse/WOLips IDE
206	206
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210	210
211	211	The following example is an almost 100% Scala WO app. In reality it is a mixed Java/Scala app:
212	212	All the EO logic and WO components are in Scala.
213		-Only the Application class is Java.
	209	+Only the Application class remains Java.
214	214
215	215	It is based on the D2W Movies example.
216	216
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218	218
219	219	=== Setup ===
220	220
221		-1. [[Install the Scala eclipse IDE>>http://www.scala-lang.org/node/94]]
222		-1. Install and start the OpenBase OBMovies database.
	217	+1. [[Install the Scala eclipse IDE>>http://www.scala-ide.org/]]
223	223	1. Right-click on Application.java and run as a WOApplication (as usual).
224	224
225		-==== EO Templates ====
	220	+Application can be made into a Scala class as well, but then you will have to create a launcher in Eclipse manually.
226	226
	222	+== EO Templates ==
	223	+
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//##
	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##
230	230	1. Change the File Names Extension to "scala"
231	231	1. In Destination Paths set the Superclass Package (e.g: base)
232	232	1. Uncheck Java under Options