INTRODUCTION TO COMPUTATIONAL MEDIA

More Organization :

Objects

Objects are an organizational tool like functions that go one step further in the same pursuit, near and dear to every programmer, REUSE of your code and ENCAPSULATION OF COMPLEXITY. Objects allow you to put functions and variables into a single package. This allows you to better compartmentalize, divide and conquer, the various challenges of your project. Crafting what functions and variable should be lumped into an object is more of an art than a science. The true beauty of these object oriented design techniques becomes very apparent when things get complicated. We will not yet go into all the nomenclature and techniques to object oreinted design such as inheritence and polymorphism. For now you will feel the benefits of having your variables and code living together one package even with simple programs.

1. Creating a Blue Print for an Object (class)
2. Creating an Object from a File

A Class is a Blue Print for an Object:

• class SnowFlake {
  int xpos; //variables
  int ypos;

SnowFlake(int _x ,int _y){ //constructor
xpos = _x; //put parameter variables into instance variables with longer scope
ypos = _y;
}

void move(){ //methods
xpos = xpos + 1;
ypos = ypos + 1;

void draw(){//methods
ellipse(xpos,ypos,10,10);
}

}

• A Class is the blue print from which objects can be made. One class can generate many copies or versions or "instances" of an object.
• A Class is another code block delimited with curly brackets. At the beginning of the code block is the word "class" followed by the name of the class.
• You can put the class definition anywhere in your processing file. (In other languages you generally to put each class definition in a separate file.)
• Inside the class will be variables (fields in object oriented speak) and functions (methods in object oriented speak).
• A Class will typically have a contructor method which is called when an object is first made. The constructor method is distinguishable because it has the same name of the class and it does not return anything (not even void). This method is usually an oportunity to set the initial state of the object, sometimes using parameter variables passed into it.
• A Class will typically have a bunch of variables. The beautiful thing is that you will get a totally independent set of these variable for each object.

Creating and Object from a Class

• SnowFlake mySnowFlake = new SnowFlake( 10 ,10);
• You use the "new" keyword to make a new object from a class. This calls a constructor method within that class.
• You can pass along parameters to the constructor method just as you would to any other function in order to establish some starting states.
• You can store the object (really a reference to the objec) in a variable. As usual the name of the variable is totally up to you.
• The type of the variable where you store the object must match the class name.
• If you need to store many object instances, you may want to use an array.