Bug using AudioUnitParameterEvent

implementation.rb

event = AudioUnitParameterEvent.new
event.scope = KAudioUnitScope_Global
event.element = 0
event.parameter = parameter
event.eventType = KParameterEvent_Ramped
event.eventValues.ramp.startBufferOffset = offset
event.eventValues.ramp.durationInFrames = frames
event.eventValues.ramp.startValue = get_parameter(parameter)
event.eventValues.ramp.endValue = value

stack trace

2014-09-09 19:33:28.444 FreesoundTouch[31115:70b] base.rb:108:in `audio_unit_parameter_event:': undefined method `ramp' for #<Boxed:0xb8fa730> (NoMethodError)
	from base.rb:78:in `ramp_to_parameter_value:'
	from effects_control.rb:98:in `set_effect_parameters:'
	from effects_control.rb:82:in `update_effect_parameters:'
	from effects_control.rb:77:in `touchesUpdated:'
	from effects_control.rb:57:in `touchesBegan:withEvent:'
2014-09-09 19:33:28.455 FreesoundTouch[31115:70b] *** Terminating app due to uncaught exception 'NoMethodError', reason: 'base.rb:108:in `audio_unit_parameter_event:': undefined method `ramp' for #<Boxed:0xb8fa730> (NoMethodError)
	from base.rb:78:in `ramp_to_parameter_value:'
	from effects_control.rb:98:in `set_effect_parameters:'
	from effects_control.rb:82:in `update_effect_parameters:'
	from effects_control.rb:77:in `touchesUpdated:'
	from effects_control.rb:57:in `touchesBegan:withEvent:'
'
*** First throw call stack:
(
	0   CoreFoundation                      0x037ef1e4 __exceptionPreprocess + 180
	1   libobjc.A.dylib                     0x0125d8e5 objc_exception_throw + 44
	2   FreesoundTouch                      0x00bbc05a _ZL10__vm_raisev + 346
	3   FreesoundTouch                      0x00bbc138 rb_vm_raise + 216
	4   FreesoundTouch                      0x00abdfb1 rb_exc_raise + 17
	5   FreesoundTouch                      0x00bba1be rb_vm_method_missing + 574
	6   FreesoundTouch                      0x00b8ddaf rb_method_missing + 31
	7   FreesoundTouch                      0x00b96f34 rb_vm_dispatch + 5060
	8   FreesoundTouch                      0x00b95a0c rb_vm_trigger_method_missing + 1004
	9   FreesoundTouch                      0x00b968eb rb_vm_dispatch + 3451
	10  FreesoundTouch                      0x003a233c vm_dispatch + 1100
	11  FreesoundTouch                      0x003ac48d rb_scope__audio_unit_parameter_event:__ + 925
	12  FreesoundTouch                      0x00bb0bed _ZL20dispatch_rimp_callerPFP11objc_objectS0_P13objc_selectorzEmS1_iPKm + 46445
	13  FreesoundTouch                      0x00b9760a rb_vm_dispatch + 6810
	14  FreesoundTouch                      0x003a233c vm_dispatch + 1100
	15  FreesoundTouch                      0x003abe90 rb_scope__ramp_to_parameter_value:__ + 976
	16  FreesoundTouch                      0x00bb0bed _ZL20dispatch_rimp_callerPFP11objc_objectS0_P13objc_selectorzEmS1_iPKm + 46445
	17  FreesoundTouch                      0x00b9760a rb_vm_dispatch + 6810
	18  FreesoundTouch                      0x009838fc vm_dispatch + 1100
	19  FreesoundTouch                      0x0098ee4b rb_scope__set_effect_parameters:__ + 1083
	20  FreesoundTouch                      0x00bb0bed _ZL20dispatch_rimp_callerPFP11objc_objectS0_P13objc_selectorzEmS1_iPKm + 46445
	21  FreesoundTouch                      0x00b9760a rb_vm_dispatch + 6810
	22  FreesoundTouch                      0x009838fc vm_dispatch + 1100
	23  FreesoundTouch                      0x0098e6f0 rb_scope__update_effect_parameters:__ + 208
	24  FreesoundTouch                      0x00bb0bed _ZL20dispatch_rimp_callerPFP11objc_objectS0_P13objc_selectorzEmS1_iPKm + 46445
	25  FreesoundTouch                      0x00b9760a rb_vm_dispatch + 6810
	26  FreesoundTouch                      0x009838fc vm_dispatch + 1100
	27  FreesoundTouch                      0x0098e516 rb_scope__touchesUpdated:__ + 566
	28  FreesoundTouch                      0x00bb0bed _ZL20dispatch_rimp_callerPFP11objc_objectS0_P13objc_selectorzEmS1_iPKm + 46445
	29  FreesoundTouch                      0x00b9760a rb_vm_dispatch + 6810
	30  FreesoundTouch                      0x009838fc vm_dispatch + 1100
	31  FreesoundTouch                      0x0098d52b rb_scope__touchesBegan:withEvent:__ + 635
	32  FreesoundTouch                      0x0098d590 __unnamed_91 + 80
	33  UIKit                               0x0240fc0b -[UIWindow _sendTouchesForEvent:] + 386
	34  UIKit                               0x024109d1 -[UIWindow sendEvent:] + 1117
	35  UIKit                               0x023e25f2 -[UIApplication sendEvent:] + 242
	36  UIKit                               0x023cc353 _UIApplicationHandleEventQueue + 11455
	37  CoreFoundation                      0x0377877f __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
	38  CoreFoundation                      0x0377810b __CFRunLoopDoSources0 + 235
	39  CoreFoundation                      0x037951ae __CFRunLoopRun + 910
	40  CoreFoundation                      0x037949d3 CFRunLoopRunSpecific + 467
	41  CoreFoundation                      0x037947eb CFRunLoopRunInMode + 123
	42  GraphicsServices                    0x05b345ee GSEventRunModal + 192
	43  GraphicsServices                    0x05b3442b GSEventRun + 104
	44  UIKit                               0x023cef9b UIApplicationMain + 1225
	45  FreesoundTouch                      0x000a530c main + 156
	46  libdyld.dylib                       0x05448701 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NoMethodError