[chuck-users] inheritance question

Voytek Lapinski voytekl at octobit.com.au
Mon Jan 23 02:18:40 EST 2017

Hi All,

Just getting into ChucK and have a language question.

I have some base classes which I have written and am struggling with how 
to get the inheritance to do what I want.

I have a class Voice, and a class Polysynth which contains an array of 
Voices as data, like so:

public class Polysynth {
         Voice voices[];
         // methods which work on the objects in 'voices',
         // ..

I want to be able to set up a patch which defines (for example) a 
MySynth_Voice (subclassing Voice) and MySynth (subclassing Polysynth). 
MySynth objects will thus contain an array of Mysynth_Voice objects. I 
want to then be able to call methods on MySynth that are defined in 
Polysynth, that uses the array of MySynth_Voices as data. The problem 
is, because they are expecting Voice objects, they aren't happy to 
receive MySynth_Voices instead (even though MySynth_Voice inherits from 
Voice). I can't cast them in the Polysynth methods that use it because 
it won't compile unless 'voices' is declared. It has to be declared as 
'Voice', and if I try to override it in the subclass (eg. "MySynth_Voice 
voices[]"), it won't compile saying saying it "has already been defined 
in super class 'Polysynth'".

I tried a bunch of different ways to do this, but the only way I can 
find to do it was to cast the voices array in the subclass as follows.

class MySynth extends Polysynth
     fun void init (int num_voices) {
         MySynth_Voice voices_temp[num_voices];
         Voice voices_temp2[num_voices];
         for (0=>int i; i < num_voices; i++) {
             voices_temp[i] $ Voice @=> voices_temp2[i];
         voices_temp2 @=> voices;

Firstly, is it possible to do this without having to do this casting 
bit? It seems like a common inheritance set up, so am wondering if I 
have just missed something. Failing that, is there a better way to do 
the casting step? I tried to do in obvious ways like 'MySynth_Voice $ 
Voice[] @=> voices' but that, and other possible permutations I could 
think of, wouldn't compile. The iterating over the whole array and doing 
each member explicitly seemed to be the only thing that worked.

It's certainly no big deal and I can live with it, but am just curious 
if there's a nicer way to do it.

Thanks all...


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