Ruby4Skype works?

I've installed ruby4skype.

I have tried a simple function with the methods found from the
ruby4skype gems' lib/sms.rb, trying to send a sms:
    @sms_targets =['+852123', '+852456']
    @sms_id, @sms_status = Skype::SMS.create @sms_targets.first,
'OUTGOING'
    @sms_body = 'testing message'

    logger.info "created #{@sms_id} #{@sms_status}: body #{@sms_body}"
    Skype::SMS.set_target_number @sms_targets

    Skype::SMS.set_body(@sms_body)
    Skype::SMS.alert_sms @sms_id , 'SEND'

HOWEVER, it failed at the very beginning " Skype::SMS.create ".

With the error: undefined method 'invoke' in the sms.rb.