If you want to overload teh accessors, you need to rename the property:

[code]
class Person(private var theAge:Int){

def age = theAge

def age_=(age:Int) = {
if(age > 120){
throw new IllegalArgumentException("Person.age=" + age + ": Too old")
} else {
theAge=age
}
}

}
[/code]

Firstly, thanks for this series of articles, I’m working my way through them now. Very helpful.

I was trying a few things out based on the examples here and the following will not compile and I would think that it should… why am i unable to overload the function/variable defined in the ‘constructor’?

Code:

class Person(var age:Int){

def age_=(age:Int) = {
if(age > 120){
throw new IllegalArgumentException(“Too old”)
}
}
}

val person = new Person(1)
println(person.age)
person.age = 50
println(person.age)

Results in:

[ERROR]com/bob/HelloWorld.scala:18: error: ambiguous reference to overloaded definition,
both method age_= in class Person of type (Int)Unit
and method age_= in class Person of type (Int)Unit
match argument types (Int)
person.age = 50

I am new to scala.

while compiling – the compiler just hangs and java processes keeps growing. Any idea what’s going on?

C:\work\scala>scala -d bin src/com/codecommit/examples/*.scala
2009-09-24 14:19:10
Full thread dump Java HotSpot(TM) Client VM (11.3-b02 mixed mode, sharing):

“Low Memory Detector” daemon prio=6 tid=0×0225d400 nid=0×10d4 runnable [0x00000000..0x00000000]
java.lang.Thread.State: RUNNABLE

“CompilerThread0″ daemon prio=10 tid=0×0225a400 nid=0xf7c waiting on condition [0x00000000..0x0444fa10]
java.lang.Thread.State: RUNNABLE

“Attach Listener” daemon prio=10 tid=0×02259800 nid=0×8a4 runnable [0x00000000..0x00000000]
java.lang.Thread.State: RUNNABLE

“Signal Dispatcher” daemon prio=10 tid=0×0224ec00 nid=0×31c waiting on condition [0x00000000..0x00000000]
java.lang.Thread.State: RUNNABLE

“Finalizer” daemon prio=8 tid=0×02246000 nid=0×1050 in Object.wait() [0x0435f000..0x0435fa68]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
– waiting on (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:116)
– locked (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:132)
at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:159)

“Reference Handler” daemon prio=10 tid=0×02244c00 nid=0xf9c in Object.wait() [0x00ddf000..0x00ddfae8]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
– waiting on (a java.lang.ref.Reference$Lock)
at java.lang.Object.wait(Object.java:485)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:116)
– locked (a java.lang.ref.Reference$Lock)

“main” prio=6 tid=0×000ea000 nid=0×1234 runnable [0x0039f000..0x0039fe28]
java.lang.Thread.State: RUNNABLE
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
– locked (a java.net.SocksSocketImpl)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:519)
at java.net.Socket.connect(Socket.java:469)
at java.net.Socket.(Socket.java:366)
at java.net.Socket.(Socket.java:209)
at scala.tools.nsc.CompileSocket.getsock$1(CompileSocket.scala:210)
at scala.tools.nsc.CompileSocket.getsock$1(CompileSocket.scala:224)
at scala.tools.nsc.CompileSocket.getOrCreateSocket(CompileSocket.scala:227)
at scala.tools.nsc.CompileSocket.getOrCreateSocket(CompileSocket.scala:232)
at scala.tools.nsc.ScriptRunner$.compileWithDaemon(ScriptRunner.scala:237)
at scala.tools.nsc.ScriptRunner$.compile$1(ScriptRunner.scala:315)
at scala.tools.nsc.ScriptRunner$.withCompiledScript(ScriptRunner.scala:350)
at scala.tools.nsc.ScriptRunner$.runScript(ScriptRunner.scala:413)
at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:168)
at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)

“VM Thread” prio=10 tid=0×02242c00 nid=0×17c0 runnable

No, it’s not as bad as all that. Scala builds are no more complicated than Java builds. In fact, all of the same tools work in just about the same way. Ant, Maven, Buildr (my personal favorite). None of them have any trouble with Scala’s unrestricted file conventions.

Nope, they’ll get a stomach ache and wonder why they need to know anything about wher the files are located. For years now I’ve not thought twice about where the files are located, and where the .class is generated. I don’t care…the IDE worries about that for me. By using Scala am I agreeing to take on the responsibility once again of wrangling files together, worrying about directory structures, and building my own make files as I once did with C/C++ apps and GCC?

public Complex(int a, int b) {
this.a = a;
this.b = b;
}

public int getA() {
return a;
}

public void setA(int a) {
this.a = a;
}

public int getB() {
return b;
}

public void setB(int b) {
this.b = b;
}
}

// …
final Complex number = new Complex(1, 0);
number.setB(12);

I totally disagree with this. Although java is verbose(which is why I am looking at scala), but I guess if I do this is scala

class Complex(var a:Int, var b:Int)

// …
val number = new Complex(1, 0)
number.b = 12

what I am saying in java terms is Complex has two public members, a and b

so in java we have

public class Complex {
public int a;
public int b;
//I dont need a contructor
}

Complex complex = new Complex();
complex.a = 12;
//…..etc
Still more verbose…but you get my point