import RPi.GPIO as gpio

class WheelEncoder:
  'Encapsulates the attributes and methods to use a wheel encoder sensor'

  inputPin = 0
  ticks = 0

  def __init__(self, inputPin):
    self.inputPin = inputPin

    gpio.setmode(gpio.BOARD)
    gpio.setup(self.inputPin, gpio.IN, pull_up_down=gpio.PUD_UP)
    gpio.add_event_detect(self.inputPin, gpio.RISING, event_callback)

  def getTicks(self):
    return self.ticks

  def resetTicks(self):
    self.ticks = 0

  def event_callback(channel):
    self.ticks += 1

Traceback (most recent call last):
  File "test-WheelEncoder.py", line 5, in <module>
    sensor = WheelEncoder(3, 10, 3)
  File "/home/pi/codes/sensors/WheelEncoder.py", line 20, in __init__
    gpio.add_event_detect(self.inputPin, gpio.RISING, event_callback)
NameError: global name 'event_callback' is not defined

gpio.add_event_detect(self.inputPin, gpio.RISING, self.event_callback)

event_callback(self, channel):