[Ghoser777]

Alright, for convenience, I made a subclass of NSMutableArray called NSMSArray (Next Step Mutable String Array). Now, all you other Coco-Java developers, try compiling this and making an instance of NSMSArray with the the static method arrayWithTokenizer.

<BLOCKQUOTE><font size="1"face="Geneva, Verdana, Arial">code:</font><HR><pre><font size=1 face=courier>
import com.apple.cocoa.foundation.*;
import com.apple.cocoa.application.*;
import java.util.StringTokenizer;


public class NSMSArray extends NSMutableArray
{

public static NSMSArray arrayWithTokenizer(StringTokenizer a)
{
String[] array = new String[a.countTokens()];
for(int i=<font color = blue>0</font>; i&lt;array.length; i++) array[i] = a.nextToken();
return new NSMSArray(array);
}

public NSMSArray(Object[] a)
{
super(a);
}

public String stringAtIndex(int i)
{
return (String)this.objectAtIndex(i);
}

public String combinedString()
{
int count = this.count();
String answer = <font color = red>""</font>;
for(int i=<font color = blue>0</font>; i&lt;count; i++) answer+=this.stringAtIndex(i);
return answer;
}

}

</font>[/code]

Notice this:

NSInvalidArgumentException: *** initialization method -initWithObjects:count: cannot be sent to an abstract object of class NSMSArray: Create a concrete instance!

After noticing this, does anyone know why this is happening or how I could fix the problem?

Thanks,
F-bacher

[Wixar]

You have to implement the primitive methods of these abstract classes. You need to implement:

addObject
insertObjectAtIndex
removeLastObject
removeObjectAtIndex
replaceObjectAtIndex

You also need to implement the primitive methods of NSArray:

count
objectAtIndex

Now you know why subclassing Cocoa abstract classes is a PITA. But since you aren't overriding any method, I can't help but wonder why you're subclassing NSMutableArray in the first place. Why not just make it an NSObject subclass?

-Peter

[Kristoff]

Why are you using a factory method here?
Why not overload the constructor?

Try this:

<BLOCKQUOTE><font size="1"face="Geneva, Verdana, Arial">code:</font><HR><pre><font size=1 face=courier>
import com.apple.cocoa.foundation.*;
import com.apple.cocoa.application.*;
import java.util.StringTokenizer;


public class NSMSArray extends NSMutableArray
{

public NSMSArray(StringTokenizer a)
{
String[] array = new String[a.countTokens()];
for(int i=<font color = blue>0</font>; i&lt;array.length; i++) array[i] = a.nextToken();
this.NSMSArray(array);
}

public NSMSArray(Object[] a)
{
super(a);
}

public String stringAtIndex(int i)
{
return (String)this.objectAtIndex(i);
}

public String combinedString()
{
int count = this.count();
String answer = <font color = red>""</font>;
for(int i=<font color = blue>0</font>; i&lt;count; i++) answer+=this.stringAtIndex(i);
return answer;
}
}
</font>[/code]

then in your code, just instantiate the NSMSArray as an object like this,
where st is some previously defined string tokenizer:

NSMSArray nsmsa = new NSMSArray(st);

[ 01-22-2002: Message edited by: Kristoff ]

[Ghoser777]

Wixar's got the key: I needed to implement all the rest of the methods in the abstract class... which would have sucked. So I just made my class a regular subclass of Object and had it implement that methods I needed, like count(), replaceObjectAtIndex(), and objectAtIndex(), and had them pass the args onto a instance of NSMutableArray.

Yeah, I could have overriden the constructor, but that doesn't really fix my problem.

Thanks,
F-bacher

[amonitzer]

Also note that you should never begin a class name with NS*, because that's reserved for Apple.

Of course that doesn't fully apply to Cocoa/Java early adaptors, because only ObjC doesn't support namespaces, but it might be better to follow the convention.

And if you want to know why NSMutableArray is an abstract class, read the docs about class clusters.