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 | Yes
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	+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).
30	30
31		-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.
32		-
33		-In addition it may offer new solutions for concurrency in WebObjects and EOF.
34		-
35	35	=== Can WebObjects be Programmed In Scala? ===
36	36
37	37	Yes. It is very simple.
...	...	@@ -48,24 +48,34 @@
48	48	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.
49	49	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.
50	50
51		-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.
52	52
53		-{{code}}
	50	+Java:
54	54
	52	+{{code value="java"}}
	53	+
55	55	public class _Talent extends EOGenericRecord {
56	56	public static final String ENTITY_NAME = "Talent";
57	57
58	58	{{/code}}
59	59
60		-In Scala:
	59	+Scala:
61	61
62	62	{{code}}
63	63
64		-object _Talent extends EOGenericRecord {
	63	+object Talent extends EOGenericRecord {
65	65	val ENTITY_NAME = "Talent"
66	66
67	67	{{/code}}
68	68
	68	+This value will be accessed exactly the same way in both languages:
	69	+
	70	+{{code}}
	71	+
	72	+Talent.ENTITY_NAME
	73	+
	74	+{{/code}}
	75	+
69	69	==== Compacted imports ====
70	70
71	71	Two lines in Java are compacted into one in Scala.
...	...	@@ -72,7 +72,7 @@
72	72
73	73	In Java:
74	74
75		-{{code}}
	82	+{{code value="java"}}
76	76
77	77	import com.webobjects.eocontrol.EOGenericRecord;
78	78	import com.webobjects.eocontrol.EORelationshipManipulation;
...	...	@@ -95,7 +95,7 @@
95	95
96	96	In Java:
97	97
98		-{{code}}
	105	+{{code value="java"}}
99	99
100	100	public class MenuHeader extends WOComponent {
101	101
...	...	@@ -116,11 +116,11 @@
116	116	==== Simplified Exception Handling ====
117	117
118	118	Scala doesn't force you to catch exceptions unlike in Java.
119		-In addition, the syntax employs Scala's very powerful pattern matching to handle different exceptions.
	126	+In addition, the syntax employs Scala's very powerful **pattern matching** to handle exceptions.
120	120
121	121	In Java:
122	122
123		-{{code}}
	130	+{{code value="java"}}
124	124
125	125	try {
126	126	EditPageInterface epi = D2W.factory().editPageForNewObjectWithEntityNamed(_manipulatedEntityName, session());
...	...	@@ -154,11 +154,54 @@
154	154
155	155	{{/code}}
156	156
	164	+==== Scala Annotations vs. Generated Accessors ====
	165	+
	166	+An example of accessing variables in WebObjects with the following languages:
	167	+
	168	+|= |= Objective-C |= Java |= Scala
	169	+|= getter | ##object name## | ##object.name()## | ##object.name##
	170	+|= setter | ##object setName:aName## | ##object.setName(aName)## | ##object.name = aName##
	171	+
	172	+Of course in Java, we may generate WebObjects classes with "get" methods as well in order to stick to convention.
	173	+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.
	174	+
	175	+E.g, in Main.scala we annotate our component keys with ##@BeanProperty## to automatically create public "set" and "get" methods.
	176	+These variables can then be accessed via //KVC//.
	177	+
	178	+{{code}}
	179	+
	180	+import scala.reflect.BeanProperty
	181	+
	182	+@BeanProperty var username = new String()
	183	+@BeanProperty var password = new String()
	184	+@BeanProperty var isAssistantCheckboxVisible = false
	185	+
	186	+{{/code}}
	187	+
	188	+== How to Use Scala Collections with EOF ==
	189	+
	190	+One of the benefits of Scala is its very powerful, concurrency-ready collection classes - primarily ##List##, ##Map## and ##Set##.
	191	+Employing these instead of ##NSArray## and ##NSDictionary## in WebObjects/EOF may be challenging.
	192	+
	193	+But one may modify the EO templates to produce API such as:
	194	+
	195	+{{code}}
	196	+
	197	+def movies: NSArray[Studio] = {
	198	+ storedValueForKey(_Studio.Keys.MOVIES).asInstanceOf[NSArray[Studio]]
	199	+}
	200	+
	201	+def moviesList: List[Studio] = {
	202	+ movies.objects.toList
	203	+}
	204	+
	205	+{{/code}}
	206	+
157	157	== How to Add Scala to a WO Project ==
158	158
159	159	{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
160	160
161		-{{note title="Note"}}
	211	+{{note}}
162	162
163	163	This is for Eclipse/WOLips IDE
164	164
...	...	@@ -166,23 +166,40 @@
166	166
167	167	== WO Scala Example ==
168	168
169		-The following example is a mixed Java/Scala version of the WO Movies D2W app.
	219	+The following example is an almost 100% Scala WO app. In reality it is a mixed Java/Scala app:
170	170	All the EO logic and WO components are in Scala.
171	171	Only the Application class is Java.
172	172
	223	+It is based on the D2W Movies example.
	224	+
173	173	{{attachments patterns=".*zip"}}{{/attachments}}
174	174
175	175	=== Setup ===
176	176
177	177	1. [[Install the Scala eclipse IDE>>http://www.scala-lang.org/node/94]]
178		-1. Install and run the OpenBase OBMovies database.
	230	+1. Install and start the OpenBase OBMovies database.
179	179	1. Right-click on Application.java and run as a WOApplication (as usual).
180	180
181	181	==== EO Templates ====
182	182
183		-See: [[Scala templates>>http://wiki.objectstyle.org/confluence/display/WOL/EOGenerator+Templates+and+Additions]]
184		-
185	185	When you create your ##.eogen## file, be sure to make the following changes in the EOGenerator Editor:
186	186
	237	+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//##
187	187	1. Change the File Names Extension to "scala"
	239	+1. In Destination Paths set the Superclass Package (e.g: base)
188	188	1. Uncheck Java under Options
	241	+
	242	+== How to Build & Deploy a WebObjects Scala Project with Ant ==
	243	+
	244	+1. [[Download>>http://www.scala-lang.org/downloads]] and install Scala
	245	+1. Set ##scala.home## (the location Scala has been installed onto) in the project ##build.properties## file
	246	+1. [[Add the scalac task and properties>>Configuring Ant to Build Scala with WebObjects]] to the ant build.xml file
	247	+1. Run from the project directory: ##sudo ant clean install##
	248	+
	249	+== Caveats ==
	250	+
	251	+{{warning}}
	252	+
	253	+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.
	254	+
	255	+{{/warning}}