CSC111 Lab 12 2011

--D. Thiebaut 09:42, 30 November 2011 (EST)

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This lab will have you play with classes and objects: the essence of Object Oriented Programming!

Part 1: A Bus

• Using the example we did in class on Tuesday as inspiration (see similar code below), create a new program that draws the bus shown above.
• Your program should have two classes:
  • class Wheel
  • class Bus

# A program with a car and a wheel class.
# 
#
"""
Objects:
Rectangle
Circle
Text
Point
Line

r = Rectangle( Point(x1, y1), Point(x2, y2) )
# object = class( information)
r.draw(win)
# .draw() is a method

class + parameters becomes the data; can apply methods, like "buttons"
"""
from graphics import *
W = 400
H = 400
# creating a class for a taxicab

#start with class for wheel; two concentric circles of different colors
class Wheel:
    def __init__(self, center, r1, r2 ): #__init__() is constructor; self is part of init; center, r1, r2 match parameters
        self.center = center
        r1, r2 = min(r1, r2), max(r1, r2)
        self.radius1 = r1
        self.radius2 = r2
        self.c1 = Circle( center, r1 )
        self.c2 = Circle( center, r2 )

    def setFill( self, col1, col2 ):
        self.c2.setFill( col1 )
        self.c1.setFill( col2 )
        
    def draw( self, win): #win matches parameter sent to draw in main
        self.c2.draw( win )
        self.c1.draw( win )

#class for car
class Car:
    def __init__(self, p1, p2 ):
        self.rect = Rectangle( p1, p2 )
        length = abs( p1.getX() - p2.getX() )
        xWheel1 = p1.getX() + length/4
        yWheel1 = p2.getY()
        xWheel2 = p2.getX() - length/4
        yWheel2 = yWheel1
        
        self.w1 = Wheel( Point(xWheel1, yWheel1), length/16, length/8 )
        self.w2 = Wheel( Point(xWheel2, yWheel2), length/16, length/8 )

    def draw( self, win ):
        self.w2.draw( win )
        self.rect.draw( win )
        self.w1.draw( win )

    def setFill( self, col1, col2, col3 ):
        self.rect.setFill( col1 )
        self.w1.setFill( col2, col3 )
        self.w2.setFill( col2, col3 )
        
def main():
    global W, H
    win = GraphWin( "Wheel Class Demo", W, H)

 
    """
    w = Wheel( Point( W/2, H/2 ), 20, 30 ) #20 and 30 are two radii
    w.setFill( "yellow", "black" ) #small circle then big circle  
    w.draw( win )
    """

    car = Car( Point( 50,50 ), Point( 250, 100 ) )
    car.setFill( "yellow", "white", "black" )
    car.draw( win )
    
    win.getMouse()
    win.close() 
   
main()

Challenge 1

• Add a for-loop that makes your bus disappear from the window. Make it go in the forward direction (i.e. left for the bus in the image above).

class Tree:
 
    def __init__( ... ):
        ...

    def draw( ... ):
        ...

    def move( ... ):
        ...

• Make your program display the tree with the bus. No need for any of them to move, but that's fine if the bus is moving out of the window...

Part 2: Trees

• Create a new class in your program called Tree. It will represent a simplified tree, with its green head of leaves, and its brown trunk.
• Make your program display the bus and the tree. It doesn't matter if the tree is in front or behind the bus.

Challenge 2

• Make the bus stand still and the tree move in the direction opposite of the bus direction.
• Make the tree move out of the window

Challenge 3

• Add another tree object. One class: two objects.
• Locate the trees in different locations so that they do not overlap (hint: you can change the constructor so that you can specify the x-coordinate of the tree object when you create it:)
• Make your program display the two trees and the bus

Challenge 4

• Make the two trees move to the right and disappear from the window

Challenge 5

• Make the trees that disappear from the right reappear on the left, giving the illusion of a real cartoon!
• For this your program will have to ask the tree object to return its x position, and if this position is larger than the width plus some offset, then the tree will have to move by a large negative dx value...

     class Tree:
         ...
         def getX( ... ):
              return ...


     def main():
         ...

         if tree.getX() > width:
              tree.move( -nnnn, 0 )