Hi Beinan: Your code is close; the uber-overloaded ChucK operator is your source of grief. Overlooking a couple of typos (i.e. "Class MyInstrument" should be "public class MyInstrument", "Public void Play" should be "fun void Play"), the real problem is lurking in line2 of my_chuck.ck: Mandolin man => dummy.m_whatever; To the compiler, it appears that you're making a UGen link, when what you really mean to be doing is assigning a *reference* of 'man' to dummy's m_whatever instance variable. And for that, you want the @=> operator instead: Mandolin man @=> dummy.m_whatever; Amended code follows. Hope this helps. - Rob // ===== File: instr.ck public class MyInstrument { StkInstrument @ m_whatever; fun void Play(dur duration) { m_whatever.noteOn(1); duration => now; m_whatever.noteOff(1); } } // ===== EOF ===== // =====- File: my_chuck.ck MyInstrument dummy; Mandolin man @=> dummy.m_whatever; dummy.m_whatever => dac; 1::second => dur d; dummy.Play(d); // ===== EOF ===== On 10 Feb 2010, at 15:40, Beinan Li 2 wrote:

Hi Chuckists,

I’d like to dynamically switch instrument as in my small code (chuck instr.ck my_chuck.ck)

// instr.ck Class MyInstrument { StkInstrument@ m_whatever;

Public void Play(dur duration) { m_whatever.noteOn(1); duration => now; m_whatever.noteOff(1); } }

// my_chuck.ck MyInstrument dummy; Mandolin man => dummy.m_whatever; Dummy.m_whatever => dac;

1::second => dur d; dummy.Play(d);

Then I got this error: [chuck](VM): NullPointerException: (UGen link) in shred[id=5:my_chuck.ck], PC=[46]

Where am I wrong with this late binding?

Thanks, Beinan _______________________________________________ chuck-users mailing list chuck-users@lists.cs.princeton.edu https://lists.cs.princeton.edu/mailman/listinfo/chuck-users

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