Computation as an Expressive Medium

1
Computation as an Expressive Medium

• Lab 3 Methods and Classes
• Annie Lausier

2
ARE YOU READY TO RUMMMMMMBBLLLLLLE?!

• Courseware!!
• A few good programming practices
• Methods Oi, whats the deal, eh?
• Classes Heres where it gets really fun
• Assignment 2!

3
Using Courseware!
http//idt.gatech.edu/mazalek/courses/fall06/lcc6
310/courseware.html
4
Drive friendly. Code friendly.

• Comments are your friend!
• Put a block of commenting at the top of each
  program that explains what it does
• Comment in code what a section will do
• Comment when you appropriate code!!
• Auto-format is also your friend!!
• Your programs will have at least three sections
• Variable declaration
• setup()
• draw()

Also known asgank, borrow, reuse, yoinks,
etc. Give due credit!
5
Methods. Reloaded.

• Methods, also known as
• Functions (methods which return something)
• Procedures (methods which dont return stuff)
• Method declaration
• Method call

void vendingMachine( int coinCents )
println("You inserted "coinCents" cents.")
int quarter 25vendingMachine(quarter)
6
Methods. Reloaded.

• Method declaration
• The method declaration is like a blueprint
• Doesn't matter if declaration is before or after
  call!
• Parameter name (e.g. coinCents) is just the name
  given to data passed into the method

parameter
void vendingMachine( int coinCents )
println("You inserted "coinCents" cents.")
7
Methods. Reloaded.

• Method call
• vendingMachine(quarter) vendingMachine(25)
• Method call must occur in either setup(), draw(),
  or another method
• You can call it as many times as you like!
• vendingMachine()s for everyone!! Hooray!

argument
int quarter 25vendingMachine(quarter)
8
Avast, Cap'n! Java Ahoy!

• Classes Theyre not just for breakfast, anymore.
• Remember that slide a couple labs ago?
• Types
• Primitives int, float, char, boolean
• Objects array, string, class

This bit of information is courtesy your memory
of things learned. Don't leave home without it.
9
Objects

• Weve worked with some objects before, like
  Arrays.
• We can make our own objects, to keep related data
  together, and methods to control that data.

10
Classes
Hey! You reused that metaphor!

• Classes are the blueprints for our new objects.
• To declare a new Class (a new type of object)

class MyToy // fields (class variables)
// methods (class functions)
11
Fields and Methods
class MySquare int xPos, yPos
MySquare(x, y) xPos x yPos y
void drawMe() rect(xPos, yPos, 50, 50)
fields
x
y
constructor
drawMe()
(one kind of method)
methods
12
Fields and Methods
class MySquare int xPos, yPos
MySquare(int x, int y) xPos x yPos y
void drawMe() rect(xPos, yPos, 50, 50)

10
10
20
90
drawMe()
drawMe()
square1
square2
MySquare square1 new MySquare(10, 10) MySquare
square2 new MySquare(20, 90)
13
Fields and Methods
class MySquare int xPos, yPos
MySquare(int x, int y) xPos x yPos y
void drawMe() rect(xPos, yPos, 50, 50)

MySquare square1 new MySquare(10, 10) MySquare
square2 new MySquare(20, 90)
square1.drawMe() square2.drawMe()
14
Arrays of Objects?

• Sure! Lets make a bunch of squares!

MySquare squares new MySquare10 //
initialize all of our squares. for (int i 0 i
i10) squares3.drawMe() // draw the 4th
square.
15
Asteroids

• Lets adapt this to make an array of Asteroids
  for our rocket from lecture.

class Asteroid //fields float rotation
0 float xPos, yPos float velocityX,
velocityY long lastDrawMillis 0
16
Asteroids

• When we create an asteroid, lets have it start
  in a random position, and move in a random
  direction.

Class Asteroid // constructor
Asteroid() xPos random(0, 400) yPos
random(0, 400) rotation random(0,
TWO_PI) velocityX sin(rotation)10 velocityY
-cos(rotation)10
17
Asteroids
Class Asteroid // draw method void
drawMe()
off to Processing!
18
OOP, we'll do it again.
The more the merrier! MUHAHAHA!

• Programming practices
• Methods, redux
• Classes, hoo-boy!

clone-o-matic
19
Assignment 2!

• A2-01 Using beginShape() and endShape(), create
  a composition with five or more vertices.
• A2-02 Using beginShape() and endShape(), create
  a composition with ten or more vertices.
• A2-03 Create an image different from A2-02, but
  using the same vertex data.
• A2-04 Write a function with one parameter and
  demonstrate it visually.
• A2-05 Write a function for drawing triangles and
  visually demonstrate its flexibility.
• A2-06 Write a function with three or more
  parameters and visually demonstrate its
  flexibility.
• A2-07 Create a dynamic animation using the cos()
  function as a generator for motion.
• A2-08 Create a dynamic animation using the cos()
  and sin() function as a generator for motion.
• A2-09 Move two visual elements across the screen
  using the random() function as a generator of
  movement. Give each element a unique nonlinear
  motion.
• A2-10 Create an event that begins when the mouse
  is pressed and ends when the mouse is released.
• A2-11 Create a responsive image that behaves
  differently when the mouse is moving and the
  mouse is dragging.
• A2-12 Create a button that changes the color of
  the background when it is clicked.
• A2-13 Program your moving elements from A2-09
  but use classes to represent the two visual
  elements.
• A2-14 Create a subclass of one of the asteroids
  classes that adds a new capability. Some examples
  of what you could do create a subclass of Rocket
  (or ArmedRocket) that shoots flame when the
  thrusters are fired and/or plays a sound when
  thrusters are fired, create a subclass of
  Asteroid that know when it's been hit (instead of
  doing this test in draw()), create a subclass of
  Asteroid that splits into two smaller Asteroids
  when it's hit.