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 Rub.
5		-This 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.
6	6
7		-Many of its features and paradigms favor multi-threading and concurrency.
8		-It could be said that Scala was designed from the ground up for concurrency.
	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.
9	9
10		-Some of these may not be unfamiliar to Objective-C and WebObjects developers. Here's a summary:
	9	+Here's a quick summary:
11	11
12		-|= |= Objective-C |= Java |= Scala
13		-|= Mutable/Immuable Datatypes | Collections //e.g: NSArray/NSMutableArray// | No | Yes
14		-|= Closures | Blocks (//Extension//) | No | Anonymous Functions
15		-|= Static variables | Yes | Yes | No
16		-|= Static methods/functions | Yes | Yes | No
17		-|= Concurrency | [[Grand Central Dispatch>>http://en.wikipedia.org/wiki/Grand_Central_Dispatch]] (//Extension//)| //Threads// |[[Actors>>http://en.wikipedia.org/wiki/Actor_model]]
18		-|= |= 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
19	19
20	20	Other notable features include:
21	21
22		-|= |= Objective-C |= Java |= Scala
23		-|= Parametered methods | Yes //e.g: addObject: to~:// | No | Yes //e.g: add(object= ,to=)//
24		-|= 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
25	25
26		-A fuller description of Scala can be found [[here>>http://en.wikipedia.org/wiki/Scala_(programming_language)]].
27		-
28	28	=== Why Use Scala? ===
29	29
30		-With Web 2.0, building concurrent WebObjects applications is a must.
31		-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.
32	32
33		-Scala offers concurrency that is (effectively) built-in to the language and is inherently thread-safe.
34		-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).
35	35
36		-In addition Scala offers itself as a solution for tasks that typically would have involved threads in a WebObjects application
37		-
38	38	=== Can WebObjects be Programmed In Scala? ===
39	39
40	40	Yes. It is very simple.
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46	46
47	47	== EOs in Scala ==
48	48
49		-=== Thread-Safe Shared Vars ===
	43	+=== Thread-Safe Shared Vars ===
50	50
51		-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.
52		-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.
53	53
	47	+So you don't have to worry about synchronizing access to shared mutable fields in a concurrent application.
	48	+
54	54	The following is an example of the use of a //Companion Object// for Talent in Scala instead of Talent static fields in Java.
55	55
56	56	Java:
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71	71
72	72	{{/code}}
73	73
	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	+
74	74	==== Compacted imports ====
75	75
76	76	Two lines in Java are compacted into one in Scala.
...	...	@@ -121,7 +121,7 @@
121	121	==== Simplified Exception Handling ====
122	122
123	123	Scala doesn't force you to catch exceptions unlike in Java.
124		-In addition, the syntax employs Scala's very powerful pattern matching to handle different exceptions.
	127	+In addition, the syntax employs Scala's very powerful **pattern matching** to handle exceptions.
125	125
126	126	In Java:
127	127
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159	159
160	160	{{/code}}
161	161
162		-==== Scala Annotations vs. Generic Accessors ====
	165	+==== Scala Annotations vs. Generated Accessors ====
163	163
164	164	An example of accessing variables in WebObjects with the following languages:
165	165
166		-|= |= Objective-C |= Java |= Scala
167		-|= getter | ##object name## | ##object.name()## | ##object.name##
168		-|= 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##
169	169
170	170	Of course in Java, we may generate WebObjects classes with "get" methods as well in order to stick to convention.
171	171	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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175	175
176	176	{{code}}
177	177
	181	+import scala.reflect.BeanProperty
	182	+
178	178	@BeanProperty var username = new String()
179	179	@BeanProperty var password = new String()
180	180	@BeanProperty var isAssistantCheckboxVisible = false
...	...	@@ -183,7 +183,7 @@
183	183
184	184	== How to Use Scala Collections with EOF ==
185	185
186		-One of the benefits of Scala is its very powerful, concurrency-ready collection classes - primarily ##List##, ##Map##, ##Seq## and ##Set##.
	191	+One of the benefits of Scala is its very powerful, concurrency-ready collection classes - primarily ##List##, ##Map## and ##Set##.
187	187	Employing these instead of ##NSArray## and ##NSDictionary## in WebObjects/EOF may be challenging.
188	188
189	189	But one may modify the EO templates to produce API such as:
...	...	@@ -190,21 +190,25 @@
190	190
191	191	{{code}}
192	192
193		-def movies: NSArray[EOGenericRecord] = {
194		- storedValueForKey(_Studio.Keys.MOVIES).asInstanceOf[NSArray[EOGenericRecord]]
	198	+import scala.collection.JavaConversions._
	199	+
	200	+def movies = {
	201	+ storedValueForKey(_Studio.Keys.MOVIES).asInstanceOf[NSArray[Movie]]
195	195	}
196		-
197		-def moviesList: List[EOGenericRecord] = {
198		- movies.objects.toList
	203	+
	204	+def moviesList = {
	205	+ movies.asInstanceOf[java.lang.Iterable[Movie]].toList
199	199	}
200	200
201	201	{{/code}}
202	202
	210	+This employs a feature of Scala known as **implicit conversions** to automagically convert a NSArray (a Java Iterable) into a Scala Iterable.
	211	+
203	203	== How to Add Scala to a WO Project ==
204	204
205	205	{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
206	206
207		-{{note title="Note"}}
	216	+{{note}}
208	208
209	209	This is for Eclipse/WOLips IDE
210	210
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214	214
215	215	The following example is an almost 100% Scala WO app. In reality it is a mixed Java/Scala app:
216	216	All the EO logic and WO components are in Scala.
217		-Only the Application class is Java.
	226	+Only the Application class remains Java.
218	218
219	219	It is based on the D2W Movies example.
220	220
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222	222
223	223	=== Setup ===
224	224
225		-1. [[Install the Scala eclipse IDE>>http://www.scala-lang.org/node/94]]
226		-1. Install and start the OpenBase OBMovies database.
	234	+1. [[Install the Scala eclipse IDE>>http://www.scala-ide.org/]]
227	227	1. Right-click on Application.java and run as a WOApplication (as usual).
228	228
229		-==== EO Templates ====
	237	+== EO Templates ==
230	230
231	231	When you create your ##.eogen## file, be sure to make the following changes in the EOGenerator Editor:
232	232
233		-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//##
	241	+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##
234	234	1. Change the File Names Extension to "scala"
235	235	1. In Destination Paths set the Superclass Package (e.g: base)
236	236	1. Uncheck Java under Options