Changes for page WebObjects with Scala

Summary

• Page properties (1 modified, 0 added, 0 removed)

Details

Page properties

Content

...	...	@@ -1,15 +1,18 @@
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
	9	+Here's a quick summary:
	10	+
8	8	|= |= Objective-C |= Java |= Scala
9	9	|= Mutable/Immuable Datatypes | Collections //e.g: NSArray/NSMutableArray// | No | Yes
10	10	|= Closures | Blocks (//Extension//) | No | Anonymous Functions
11	11	|= Static variables | Yes | Yes | No
12		-|= Static methods/functions | Yes | Yes | No
	15	+|= Static methods or functions| Yes | Yes | No
13	13	|= Concurrency | [[Grand Central Dispatch>>http://en.wikipedia.org/wiki/Grand_Central_Dispatch]] (//Extension//)| //Threads// |[[Actors>>http://en.wikipedia.org/wiki/Actor_model]]
14	14	|= |= Weakly Typed |=--Strongly Typed--|= Strongly Typed
15	15
...	...	@@ -19,18 +19,13 @@
19	19	|= Parametered methods | Yes //e.g: addObject: to~:// | No | Yes //e.g: add(object= ,to=)//
20	20	|= 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		-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).
31	31
32		-In addition it may offer new solutions for concurrency in WebObjects and EOF.
33		-
34	34	=== Can WebObjects be Programmed In Scala? ===
35	35
36	36	Yes. It is very simple.
...	...	@@ -47,20 +47,22 @@
47	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	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.
49	49
50		-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.
51	51
52		-{{code}}
	50	+Java:
53	53
	52	+{{code value="java"}}
	53	+
54	54	public class _Talent extends EOGenericRecord {
55	55	public static final String ENTITY_NAME = "Talent";
56	56
57	57	{{/code}}
58	58
59		-In Scala:
	59	+Scala:
60	60
61	61	{{code}}
62	62
63		-object _Talent extends EOGenericRecord {
	63	+object Talent extends EOGenericRecord {
64	64	val ENTITY_NAME = "Talent"
65	65
66	66	{{/code}}
...	...	@@ -71,7 +71,7 @@
71	71
72	72	In Java:
73	73
74		-{{code}}
	74	+{{code value="java"}}
75	75
76	76	import com.webobjects.eocontrol.EOGenericRecord;
77	77	import com.webobjects.eocontrol.EORelationshipManipulation;
...	...	@@ -94,7 +94,7 @@
94	94
95	95	In Java:
96	96
97		-{{code}}
	97	+{{code value="java"}}
98	98
99	99	public class MenuHeader extends WOComponent {
100	100
...	...	@@ -115,11 +115,11 @@
115	115	==== Simplified Exception Handling ====
116	116
117	117	Scala doesn't force you to catch exceptions unlike in Java.
118		-In addition, the syntax employs Scala's very powerful pattern matching to handle different exceptions.
	118	+In addition, the syntax employs Scala's very powerful **pattern matching** to handle exceptions.
119	119
120	120	In Java:
121	121
122		-{{code}}
	122	+{{code value="java"}}
123	123
124	124	try {
125	125	EditPageInterface epi = D2W.factory().editPageForNewObjectWithEntityNamed(_manipulatedEntityName, session());
...	...	@@ -153,9 +153,33 @@
153	153
154	154	{{/code}}
155	155
	156	+==== Scala Annotations vs. Generated Accessors ====
	157	+
	158	+An example of accessing variables in WebObjects with the following languages:
	159	+
	160	+|= |= Objective-C |= Java |= Scala
	161	+|= getter | ##object name## | ##object.name()## | ##object.name##
	162	+|= setter | ##object setName:aName## | ##object.setName(aName)## | ##object.name = aName##
	163	+
	164	+Of course in Java, we may generate WebObjects classes with "get" methods as well in order to stick to convention.
	165	+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.
	166	+
	167	+E.g, in Main.scala we annotate our component keys with ##@BeanProperty## to automatically create public "set" and "get" methods.
	168	+These variables can then be accessed via //KVC//.
	169	+
	170	+{{code}}
	171	+
	172	+import scala.reflect.BeanProperty
	173	+
	174	+@BeanProperty var username = new String()
	175	+@BeanProperty var password = new String()
	176	+@BeanProperty var isAssistantCheckboxVisible = false
	177	+
	178	+{{/code}}
	179	+
156	156	== How to Use Scala Collections with EOF ==
157	157
158		-One of the benefits of Scala is its very powerful, concurrency-ready collection classes - primarily ##List##, ##Map##, ##Seq## and ##Set##.
	182	+One of the benefits of Scala is its very powerful, concurrency-ready collection classes - primarily ##List##, ##Map## and ##Set##.
159	159	Employing these instead of ##NSArray## and ##NSDictionary## in WebObjects/EOF may be challenging.
160	160
161	161	But one may modify the EO templates to produce API such as:
...	...	@@ -195,15 +195,21 @@
195	195	=== Setup ===
196	196
197	197	1. [[Install the Scala eclipse IDE>>http://www.scala-lang.org/node/94]]
198		-1. Install and run the OpenBase OBMovies database.
	222	+1. Install and start the OpenBase OBMovies database.
199	199	1. Right-click on Application.java and run as a WOApplication (as usual).
200	200
201	201	==== EO Templates ====
202	202
203		-See: [[Scala templates>>http://wiki.objectstyle.org/confluence/display/WOL/EOGenerator+Templates+and+Additions]]
204		-
205	205	When you create your ##.eogen## file, be sure to make the following changes in the EOGenerator Editor:
206	206
207		-1. Point to the local .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//##
208	208	1. Change the File Names Extension to "scala"
	231	+1. In Destination Paths set the Superclass Package (e.g: base)
209	209	1. Uncheck Java under Options
	233	+
	234	+== How to Build & Deploy a WebObjects Scala Project with Ant ==
	235	+
	236	+1. [[Download>>http://www.scala-lang.org/downloads]] and install Scala
	237	+1. Set ##scala.home## (the location Scala has been installed onto) in the project ##build.properties## file
	238	+1. [[Add the scalac task and properties>>Configuring Ant to Build Scala with WebObjects]] to the ant build.xml file
	239	+1. Run from the project directory: ##sudo ant clean install##