RubyMotion Throttler *currently not working*

alerter.rb

class Alerter
  def alert(message)
    NSLog("#{message}!")
  end
end

caller.rb

class Throttler
  attr_reader :object, :seconds

  def initialize(object, seconds)
    @object  = object
    @seconds = seconds
  end

  def call(selector, *args)
    unless blocked[selector]
      blocked[selector] = true

      method_signature = object.methodSignatureForSelector(selector)

      NSInvocation.invocationWithMethodSignature(method_signature).tap do |invocation|
        invocation.setSelector(selector)
        invocation.setTarget(object)

        args.each_with_index do |object, index|
          pointer    = Pointer.new('@')
          pointer[0] = argument

          invocation.setArgument(pointer, atIndex: index)
        end

        invocation.invoke
      end

      performSelector('unblock:', withObject: selector, afterDelay: seconds)
    end
  end

  private

  def unblock(selector)
    blocked.delete(selector)
  end

  def blocked
    @blocked ||= {}
  end
end

stacktrace.txt

     Build ./build/iPhoneSimulator-7.0-Development
   Compile ./app/throttler.rb
      Link ./build/iPhoneSimulator-7.0-Development/debounce.app/debounce
    Create ./build/iPhoneSimulator-7.0-Development/debounce.app/Info.plist
    Create ./build/iPhoneSimulator-7.0-Development/debounce.dSYM
  Simulate ./build/iPhoneSimulator-7.0-Development/debounce.app
2014-02-10 15:22:51.496 debounce[62164:80b] Cannot find executable for CFBundle 0x8b674e0 </Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator7.0.
sdk/System/Library/AccessibilityBundles/CertUIFramework.axbundle> (not loaded)
2014-02-10 15:22:51.563 debounce[62164:80b] -[String alert]: unrecognized selector sent to instance 0x8b44850
(main)> 2014-02-10 15:22:51.857 debounce[62164:80b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[String alert]: unrecognized selector sent to instance 0x8b44850'
*** First throw call stack:
(
        0   CoreFoundation                      0x01d885e4 __exceptionPreprocess + 180
        1   libobjc.A.dylib                     0x001d08b6 objc_exception_throw + 44
        2   CoreFoundation                      0x01e25903 -[NSObject(NSObject) doesNotRecognizeSelector:] + 275
        3   CoreFoundation                      0x01d7890b ___forwarding___ + 1019
        4   CoreFoundation                      0x01d784ee _CF_forwarding_prep_0 + 14
        5   CoreFoundation                      0x01d7cd1d __invoking___ + 29
        6   CoreFoundation                      0x01d7cc2a -[NSInvocation invoke] + 362
        7   debounce                            0x00014713 __unnamed_96 + 67
        8   debounce                            0x00108491 rb_vm_dispatch + 4577
        9   debounce                            0x0000bbdc vm_dispatch + 1100
        10  debounce                            0x00012dc7 rb_scope__call:__block__ + 727
        11  debounce                            0x001161bf _ZL20dispatch_bimp_callerPFP11objc_objectS0_P13objc_selectorzEmS1_mP11rb_vm_blockiPKm + 46351
        12  debounce                            0x00109acc _ZL13vm_block_evalP7RoxorVMP11rb_vm_blockP13objc_selectormiPKm + 1244
        13  debounce                            0x00109cc4 rb_vm_yield_args + 84
        14  debounce                            0x000fe753 rb_yield + 67
        15  debounce                            0x00082640 rb_obj_tap + 16
        16  debounce                            0x0012183f _ZL20dispatch_rimp_callerPFP11objc_objectS0_P13objc_selectorzEmS1_iPKm + 46303
        17  debounce                            0x00108773 rb_vm_dispatch + 5315
        18  debounce                            0x0000bbdc vm_dispatch + 1100
        19  debounce                            0x00012990 rb_scope__call:__ + 896
        20  debounce                            0x0012183f _ZL20dispatch_rimp_callerPFP11objc_objectS0_P13objc_selectorzEmS1_iPKm + 46303
        21  debounce                            0x00108773 rb_vm_dispatch + 5315
        22  debounce                            0x0001575c vm_dispatch + 1100
        23  debounce                            0x0001c0ce rb_scope__viewDidLoad__ + 558
        24  debounce                            0x0001c108 __unnamed_9 + 24
        25  UIKit                               0x0070b318 -[UIViewController loadViewIfRequired] + 696
        26  UIKit                               0x0070b5b4 -[UIViewController view] + 35
        27  UIKit                               0x006339fd -[UIWindow addRootViewControllerViewIfPossible] + 66
        28  UIKit                               0x00633d97 -[UIWindow _setHidden:forced:] + 312
        29  UIKit                               0x0063402d -[UIWindow _orderFrontWithoutMakingKey] + 49
        30  UIKit                               0x0e378c66 -[UIWindowAccessibility(SafeCategory) _orderFrontWithoutMakingKey] + 77
        31  UIKit                               0x0063e89a -[UIWindow makeKeyAndVisible] + 65
        32  debounce                            0x00014713 __unnamed_96 + 67
        33  debounce                            0x00108491 rb_vm_dispatch + 4577
        34  debounce                            0x0001d54c vm_dispatch + 1100
        35  debounce                            0x000243c1 rb_scope__initialize_main_controller__ + 913
        36  debounce                            0x0012183f _ZL20dispatch_rimp_callerPFP11objc_objectS0_P13objc_selectorzEmS1_iPKm + 46303
        37  debounce                            0x00108773 rb_vm_dispatch + 5315
        38  debounce                            0x0001d54c vm_dispatch + 1100
        39  debounce                            0x00023da7 rb_scope__application:didFinishLaunchingWithOptions:__ + 119
        40  debounce                            0x00023e1f __unnamed_11 + 95
        41  UIKit                               0x005f1355 -[UIApplication _handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 309
        42  UIKit                               0x005f1b95 -[UIApplication _callInitializationDelegatesForURL:payload:suspended:] + 1536
        43  UIKit                               0x005f63a8 -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 824
        44  UIKit                               0x0060a87c -[UIApplication handleEvent:withNewEvent:] + 3447
        45  UIKit                               0x0060ade9 -[UIApplication sendEvent:] + 85
        46  UIKit                               0x005f8025 _UIApplicationHandleEvent + 736
        47  GraphicsServices                    0x03a0e2f6 _PurpleEventCallback + 776
        48  GraphicsServices                    0x03a0de01 PurpleEventCallback + 46
        49  CoreFoundation                      0x01d03d65 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 53
        50  CoreFoundation                      0x01d03a9b __CFRunLoopDoSource1 + 523
        51  CoreFoundation                      0x01d2e77c __CFRunLoopRun + 2156
        52  CoreFoundation                      0x01d2dac3 CFRunLoopRunSpecific + 467
        53  CoreFoundation                      0x01d2d8db CFRunLoopRunInMode + 123
        54  UIKit                               0x005f5add -[UIApplication _run] + 840
        55  UIKit                               0x005f7d3b UIApplicationMain + 1225
        56  debounce                            0x00002d9c main + 156
        57  libdyld.dylib                       0x02fd570d start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

view_controller.rb

class ViewController < UIViewController
  def viewDidLoad
    super

    alerter = Alerter.new
    throttler = Throttler.new(alerter, 0.5).call(:alert, 'Error')
  end
end