I just learned basics in processing and need some help...

I don't understand how to give a behavior to an object: I want my draw function to execute the "update function" of each object of the class I create....
I want to avoid this:
void draw(){
  object1.update();
  object2.update();
  object3.update();
}
and do something like that but inside the constructor:

class blabla{
    blabla(){
      this.draw(){
          // do something each new frame
         }
    }
 }

I hope you understand what I mean (need some help in english too!).

If you understand actionscript here is the code I want to "translate" in processing:

   movieclip.onEnterFrame = function(){
         do something each new frame;
         }
this function is like the draw function in processing but can be written inside the class constructor... and so be execute for each object created...

Thank you in advance....

Here's a way to do it without Vectors. It's longer, but more beginner friendly IMO.


Code:

class myObj
{
  float x;
  float y;
  myObj()
  {
   //constructor sets the defaults
   x=random(200);
   y=random(200);
  }
  void drawObjects()
  {
    ellipse(x,y,20,20);
  }
}

//make an array of these
myObject things[]=new myObject[10];

void setup()
{
  //construct them
  for(int i=0;i<things.length;i++)
  {
    things[i]=new myObject();
  }
}

void draw()
{
  //draw them
  for(int i=0;i<things.length;i++)
  {
    things[i].draw();
  }
}

 

thank you guys,...

I don't really get the syntax for the vector but I like the second version .... thanks a lot.

chau, you're on the right track. the (mc) in ((mc)mcs.get(i)).draw(); is a way of casting an object to a correct type, just like (float)foobar is. however, a float or an int are simple data types and objects are more complicated.

the Vector class stores objects as instances of the superclass Object (which all classes are descended from). when you retrieve them from the Vector using the mcs.get(i) syntax you need to typecast them back to the type of object you want them to be. this is easy if you know that all objects in the Vector are of the same class.

so ((mc)mcs.get(i)).draw(); tells the Vector "mcs" to return the object at index "i", cast it to class "mc" and call its draw() command. this is a kind of shorthand which is perfectly valid but difficult to read if you don't understand how objects and Vectors work.

Vectors are a class within Java. Processing makes Java applets for you using an open source library of handy gubbinz that makes learning C style object orientated languages very easy for you. There's a whole host of hidden functions available here

Personally I don't use Vectors, I use a method which involves something called a deep-copy. You make an empty array that's a bit longer (call it temp for example) and then deep-copy you old array into the new one. In that extra slot on the end you just put in the last bit of the old array again.

I read a post where it is said that the deep-copy method is faster than Vectors. Here's an example of some deep-copy methods you could adapt for your work. They're based on the array transforming methods in the reference.

Code:

//2D vector path class (not to be confused with Java's "Vector") and methods
class Vec2{
  float x,y;
  Vec2(){}
  Vec2(float x, float y){
    this.x = x;
    this.y = y;
  }
}

//array functions
Vec2 [] addVec2(Vec2 [] vectors, Vec2 newVector) {  
  Vec2 [] temp = new Vec2[vectors.length + 1];  
  System.arraycopy(vectors, 0, temp, 0, vectors.length);  
  temp[vectors.length] = newVector;   
  return temp;
}
Vec2 [] concatVec2(Vec2 [] vectors, Vec2 [] addVectors) {  
  Vec2 [] temp = new Vec2[vectors.length + addVectors.length];  
  System.arraycopy(vectors, 0, temp, 0, vectors.length);  
  System.arraycopy(addVectors, 0, temp, vectors.length, addVectors.length);   
  return temp;
}
Vec2 [] subsetVec2(Vec2 [] vectors, int offset, int len) {  
  Vec2 [] temp = new Vec2[len];  
  System.arraycopy(vectors, offset, temp, 0, len);    
  return temp;
}
 

Usage would be along the lines of:

myPath = addVec2(myPath, newCoords);

Yes you have to make it all yourself in Processing. But at least you can have multi-dimensional arrays of anything and everything and don't have to dicker with that _root["clipName" + cantPutMovieClipInArraySoHeresANumberTackedOnTheEndOfAString].stuff() that's driving me up the wall in Flash right now.

cello wrote on Jan 14^th, 2006, 2:50am:


Ok children, let's play nice.

More seriously, I've only recently been reading up on Java and learning about the casting problems when playing with dynamic arrays, but I find this whole business of "loosing" the class of the object when storing it in the Vector array awfully messy. Of course if you put it there in the first place you should able to figure out its cast, but this is not always the case.

In Objective-c there's a nice little method for asking an object its ilk, that way you can make loosely typed interfaces, which is a pretty damn powerful thing. Someone will probably jump up at this point and shout, "you can do that too in Java", and of course I'm all ears.

But whatever the case, I'm pretty frustrated with the Java classes for lists, arrays, vectors, call them what you will. I find it all horridly clumsy and very computer-science-ish. Arrays are so essential to any interresting work -- and dynamic arrays even more important -- that I feel so cramped working inside of Processing/Java's arrays. It feels like the days before Garbage Collection. I see that Sun keeps adding new forms of arrays with each new Java version, but they look just as difficult, each one. Can anyone point me to a nice, clean, dynamic array class in Java

I've also been spoiled with Lingo's brilliant #property lists which are similar to "key-valued pairs" in Objective-C and "maps" in Java. They're so easy to write, and so *readable* which is often more important for me that getting a clock-cycle or two out of code.

I also have become addicted to growing arrays inside of arrays almost infinitely in Lingo, often I get down to about about a dozen levels. It allows me to do some pretty subtle things with the user's interactions. This is just too messy in Java.

Or maybe I just don't have enough experience with all this yet.

cello wrote on Jan 15^th, 2006, 1:09am:


Ah, but I'm using the Processing IDE. Easy to use...

cello wrote on Jan 15^th, 2006, 1:09am:


I'm not used to this syntax. I'll check it out.

Hrmm, where on earth did I read that deep-copy was faster. I've run a test - the results say Vector();
Code:

int iter=10000;
Vec2 [] test = new Vec2[1];
Vec2 temp;
Vector best;
void setup(){
  test[0] = new Vec2(0,0);
  temp = new Vec2(0,0);
  best = new Vector();
  int t0=millis();
  for(int i=0; i<iter; i++) best.add(temp);
  println("Vector method : "+(millis()-t0)+"ms");
  t0=millis();
  for(int i=0; i<iter; i++) test = addVec2(test, temp);
  println("deep-copy method : "+(millis()-t0)+"ms");
}
class Vec2{
  float x,y;
  Vec2(){
  }
  Vec2(float x, float y){
    this.x = x;
    this.y = y;
  }
}
Vec2 [] addVec2(Vec2 [] vectors, Vec2 newVector) {  
  Vec2 [] temp = new Vec2[vectors.length + 1];  
  System.arraycopy(vectors, 0, temp, 0, vectors.length);  
  temp[vectors.length] = newVector;   
  return temp;
}