If you're talking about defining your own object types via classes, you need to make sure that the .ck file containing your defined class gets added to the virtual machine first. The best way to do this is to instantiate the VM in one terminal by using the comand chuck --loop. After that, open another terminal and type chuck + Class.ck (replace class with whatever your filename is). Then go ahead and add the client (whatever file is utilizing your defined class). I'm not sure if this is what you're asking, and I'm new to ChucK myself, but hopefully this gets you started on the right track. The other way is to just type "chuck Service.ck client.ck" or whatever (it is necessary that the class containing your user-defined object is first). This works as well, but it's not as flexible on-the-fly as running chuck --loop.
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From: henrique matias