...
Scala is a modern, multi-paradigm JVM language that is most often compared to Groovy, Clojure or and Erlang. Its functional language foundations and built-in Actors 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. 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:
| Objective-C | Java | Scala |
|---|---|---|---|
Immutability | Collections Partial - via collections e.g: NSArray/NSMutableArray | No | Yes |
Closures | Yes - via Blocks (Extension) | No | Yes - via Anonymous Functions |
Static variables | Yes | Yes | No |
Static methods or functions | Yes | Yes | No |
Concurrency | Yes - via Grand Central Dispatch (Extension) | Yes - via Threads | Yes - via Actors |
| Weakly Typed | Strongly Typed | Strongly Typed |
...
| Objective-C | Java | Scala |
|---|---|---|---|
Parametered methods | Yes e.g: addObject: to: | No | Yes e.g: add(object= ,to=) |
Class composition | Yes - via Categories | Yes - via Interfaces | Yes - via Traits |
Why Use Scala?
For WebObjects developers, Scala offers itself as a powerful, safe and easy-to-use solution for concurrent computing. (In other words, Scala Actors can be used for problems that would have normally required threads).
...
| Code Block | ||||
|---|---|---|---|---|
| ||||
public class _Talent extends EOGenericRecord { public static final String ENTITY_NAME = "Talent"; } |
Scala:
| Code Block |
|---|
object Talent {
val ENTITY_NAME = "Talent"
}
|
This value will be accessed exactly the same way in both languages:
...
| Code Block | ||||
|---|---|---|---|---|
| ||||
public class MenuHeader extends WOComponent {
public MenuHeader(WOContext aContext) {
super(aContext);
}
}
|
In Scala:
| Code Block |
|---|
class MenuHeader(context: WOContext) extends WOComponent(context: WOContext) {
|
Simplified Exception Handling
...
Scala Annotations vs. Generated Accessors
An Here's an example of accessing variables in WebObjects with the following languages:
| Objective-C | Java | Scala | |||
|---|---|---|---|---|---|---|
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="7b116617-af9a-44fb-a822-95a304cc415b"><ac:plain-text-body><![CDATA[ | getter | | |
| ]]></ac:plain-text-body></ac:structured-macro> | <ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="34df408c-6156-46c7-ae96-38f9338acc10"><ac:plain-text-body><![CDATA[ |
setter | | |
| ]]></ac:plain-text-body></ac:structured-macro>
Of course in Java, we may generate WebObjects classes with "get" methods as well in order to stick to convention.
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.
...
| Attachments | ||
|---|---|---|
|
Setup
- Install the Scala eclipse IDE
- Right-click on Application.java and run as a WOApplication (as usual).
...