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://www.scala-lang.org/]] is a modern, multi-paradigm JVM language that is most often compared to [[Groovy>>http://en.wikipedia.org/wiki/Groovy_(programming_language)]], [[Clojure>>http://en.wikipedia.org/wiki/Clojure]] or [[Erlang>>http://en.wikipedia.org/wiki/Erlang_(programming_language)]]. Its [[functional language>>http://en.wikipedia.org/wiki/Functional_programming]] foundations and built-in [[Actors>>http://en.wikipedia.org/wiki/Actor_model]] library make it especially attractive for concurrent computing. (Scala is an abbreviation for "scalable" hinting at its design goals). In this day and age of multi-core processors concurrent computing can not 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:
	5	+Many of the design features of Scala have been chosen with concurrency in mind, some of which may not be unfamiliar to Objective-C or WebObjects developers. Here's a summary:
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
	7	+|= |= Objective-C |= Java |= Scala
	8	+|= Immutability | Partial - via collections //e.g: NSArray/NSMutableArray// | No | Yes
	9	+|= Closures | Yes - via Blocks (//Extension//) | No | Yes - via Anonymous Functions
	10	+|= Static variables | Yes | Yes | No
	11	+|= Static methods or functions | Yes | Yes | No
	12	+|= Concurrency | Yes - via [[Grand Central Dispatch>>http://en.wikipedia.org/wiki/Grand_Central_Dispatch]] (//Extension//) | //Yes - via Threads// | Yes - via [[Actors>>http://en.wikipedia.org/wiki/Actor_model]]
	13	+|= |= Weakly Typed |= --Strongly Typed-- |= Strongly Typed
15	15
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
	17	+|= |= Objective-C |= Java |= Scala
	18	+|= Parametered methods | Yes //e.g: addObject: to~:// | No | Yes //e.g: add(object= ,to=)//
	19	+|= Class composition | Yes - via Categories | Yes - via Interfaces | Yes - via [[Traits>>http://en.wikipedia.org/wiki/Trait_(computer_science)]]
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.
	23	+For WebObjects developers, Scala offers itself as a powerful, safe and easy-to-use solution for [[concurrent computing>>Building Concurrent Applications with WebObjects and Scala]]. (In other words, Scala Actors can be used for problems that would have normally required threads).
28	28
29		-Scala offers concurrency that is (effectively) built-in to the language and is inherently thread-safe.
	25	+=== Can WebObjects be Programmed In Scala? ===
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.
	27	+Yes. It is very simple.
	28	+By virtue of being a JVM-language, Scala compiles to java bytecode.
32	32
33		-In addition it may offer new solutions for concurrency in WebObjects and EOF.
	30	+Furthermore, being a multi-paradigm language grants Scala easy WebObjects-interoperability.
34	34
35		-=== Can WebObjects be Programmed In Scala? ===
	32	+===== Caveats =====
36	36
37		-Yes. It is very simple.
38		-Scala compiles to java bytecode. Hence using it with WebObjects is fairly straightforward.
	34	+Legacy tool support is often cited as a weak point. The [[Eclipse Scala plugin>>http://www.scala-ide.org]] has been found to be slow at times and sometimes buggy.
39	39
40	40	= WebObjects In Scala =
41	41
...	...	@@ -43,36 +43,46 @@
43	43
44	44	== EOs in Scala ==
45	45
46		-=== Thread-Safe Shared Vars ===
	42	+=== Thread-Safe Shared Vars ===
47	47
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		-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.
	44	+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.
50	50
51		-In Java:
	46	+You don't have to worry about synchronizing access to shared mutable fields in a concurrent application.
	47	+(This is not however true when for example you have a ##val## declared as a ##NSMutableArray##. You will still have to synchronize when adding to or removing from this mutable field).
52	52
53		-{{code}}
	49	+The following is an example of the use of a //Companion Object// for Talent in Scala instead of Talent static fields in Java.
54	54
	51	+Java:
	52	+
	53	+{{code value="java"}}
	54	+
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:
	60	+Scala:
61	61
62	62	{{code}}
63	63
64		-object _Talent extends EOGenericRecord {
	64	+object Talent {
65	65	val ENTITY_NAME = "Talent"
66	66
67	67	{{/code}}
68	68
69		-==== Compacted imports ====
	69	+This value will be accessed exactly the same way in both languages:
70	70
71		-Two lines in Java are compacted into one in Scala.
	71	+{{code}}
72	72
	73	+Talent.ENTITY_NAME
	74	+
	75	+{{/code}}
	76	+
	77	+==== Compacted imports ====
	78	+
73	73	In Java:
74	74
75		-{{code}}
	81	+{{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}}
	104	+{{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.
	125	+In addition, the syntax employs Scala's very powerful **pattern matching** to handle exceptions.
120	120
121	121	In Java:
122	122
123		-{{code}}
	129	+{{code value="java"}}
124	124
125	125	try {
126	126	EditPageInterface epi = D2W.factory().editPageForNewObjectWithEntityNamed(_manipulatedEntityName, session());
...	...	@@ -154,35 +154,79 @@
154	154
155	155	{{/code}}
156	156
157		-== How to Add Scala to a WO Project ==
	163	+==== Scala Annotations vs. Generated Accessors ====
158	158
159		-{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
	165	+An example of accessing variables in WebObjects with the following languages:
160	160
161		-{{note title="Note"}}
	167	+|= |= Objective-C |= Java |= Scala
	168	+|= getter | ##object name## | ##object.name()## | ##object.name##
	169	+|= setter | ##object setName:aName## | ##object.setName(aName)## | ##object.name = aName##
162	162
163		-This is for Eclipse/WOLips IDE
	171	+Of course in Java, we may generate WebObjects classes with "get" methods as well in order to stick to convention.
	172	+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.
164	164
165		-{{/note}}
	174	+E.g, in Main.scala we annotate our component keys with ##@BeanProperty## to automatically create public "set" and "get" methods.
	175	+These variables can then be accessed via //KVC//.
166	166
	177	+{{code}}
	178	+
	179	+import scala.reflect.BeanProperty
	180	+
	181	+@BeanProperty var username = new String()
	182	+@BeanProperty var password = new String()
	183	+@BeanProperty var isAssistantCheckboxVisible = false
	184	+
	185	+{{/code}}
	186	+
	187	+== How to Use Scala Collections with EOF ==
	188	+
	189	+To use the Scala Collections API with an NSArray or NSDictionary you simply need to add an import:
	190	+
	191	+{{code value="java"}}
	192	+
	193	+import scala.collection.JavaConversions._
	194	+
	195	+{{/code}}
	196	+
	197	+After that, you may 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.
	198	+
	199	+== How to Add Scala to a WO Project (in Eclipse) ==
	200	+
	201	+{{include value="WOL:Adding Scala Support to a WOLips Project"}}{{/include}}
	202	+
167	167	== WO Scala Example ==
168	168
169		-The following example is a mixed Java/Scala version of the WO Movies D2W app.
	205	+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		-Only the Application class is Java.
	207	+Only the Application class remains Java.
172	172
	209	+It is based on the D2W Movies example.
	210	+
173	173	{{attachments patterns=".*zip"}}{{/attachments}}
174	174
175	175	=== Setup ===
176	176
177		-1. [[Install the Scala eclipse IDE>>http://www.scala-lang.org/node/94]]
178		-1. Install and run the OpenBase OBMovies database.
	215	+1. [[Install the Scala eclipse IDE>>http://www.scala-ide.org/]]
179	179	1. Right-click on Application.java and run as a WOApplication (as usual).
180	180
181		-==== EO Templates ====
	218	+{{note}}
182	182
183		-See: [[Scala templates>>http://wiki.objectstyle.org/confluence/display/WOL/EOGenerator+Templates+and+Additions]]
	220	+Application can be made into a Scala class as well, but then you will have to create a launcher in Eclipse manually.
184	184
	222	+{{/note}}
	223	+
	224	+== EO Templates ==
	225	+
185	185	When you create your ##.eogen## file, be sure to make the following changes in the EOGenerator Editor:
186	186
	228	+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"
	230	+1. In Destination Paths set the Superclass Package (e.g: base)
188	188	1. Uncheck Java under Options
	232	+
	233	+== How to Build & Deploy a WebObjects Scala Project with Ant ==
	234	+
	235	+1. [[Download>>http://www.scala-lang.org/downloads]] and install Scala
	236	+1. Set ##scala.home## (the location Scala has been installed onto) in the project ##build.properties## file
	237	+1. [[Add the scalac task and properties>>Configuring Ant to Build Scala with WebObjects]] to the ant build.xml file
	238	+1. Run from the project directory: ##sudo ant clean install##