Create multiple variables using for loop

Programming Questions

cherub.ro..

Create multiple variables using for loop

in Programming Questions • 10 months ago

Hello.

I'm a noob, so please make answers as simple as possible. I want to create a program where there are balls moving randomly (done this bit). I've made the balls as a separate class, so I have to make a new variable every time I want to make a ball. This is fine for a couple of objects, but I want 20 balls (and at some point I will also want to vary this number).

I thought perhaps I could make a for loop that creates the variables? Something like...

for (i=1; i<21; i++) {

Ball ball[i];

}

void setup () {

for (i=1; i<21; i++) {

ball[i] = new Ball();

}

So this would make 20 balls, calling each one ball1, ball2, ball3 etc. How can I do this? If I cannot use a for loop, what other way would be good for making many variables like this?

Thank you!

Replies(3)

timpulver

Re: Create multiple variables using for loop

10 months ago

It's done exactly as you said yourself - use an array!

int nBalls = 20;
Ball[] balls;
void setup(){
size(500, 500);
balls = new Ball[nBalls];
for(int i=0; i<nBalls; i++){
balls[i] = new Ball();
}
}
void draw(){
for(int i=0; i<nBalls; i++){
fill(255);
// every 5th ball should be red
if(i%5 == 0) fill(255, 0, 0);
balls[i].draw();
}
}
class Ball{
float x, y;
Ball(){
x = random(0, width);
y = random(0, height);
}
void draw(){
ellipse(x, y, 10, 10);
}
}

GoToLoop

Re: Create multiple variables using for loop

10 months ago

Once you initialize each element of your array of class Ball using new like you already did @ setup():

void setup () {

for (i=0; i<ball.length; i++) {

ball[i] = new Ball();

}

You don't re-declare them again w/ Ball as you did:

for (i=0; i<ball.length; i++) {

wrong -> Ball ball[i];

}

Instead, you just use the instance array ( ball[] ) which represents the class Ball, along w/calling its methods:

for (i=0; i<ball.length; i++) {

      ball[i].method1();
      ball[i].method2();
      ball[i].method3();

}

Where method1(), method2(), method3() and so on, are functions you create inside class Ball to move and animate the object!

Also, take a look on a similar example in this link -> Bouncing Balloons