What does add() do?

Processing Beginners
1

So I have a code:

class Projectile extends PVector
{
  PVector velocity;
 
  Projectile(PVector loc, PVector vel)
  {
    super(loc.x, loc.y);
    velocity = vel;
  }
 
  void Display()
  {   
    add(velocity); // what does this do?
    
    fill(0, 0, 255);
    ellipse(x, y, 3, 3);
  }
}

I found this on a example I saw. It creates a bullet, and shoots it towards the mouse. The example didn’t explain the code, so I had to figure out what I does. But I’m stuck on this part. When it says add(velocity), it confuses me. What are you adding velocity too?

2

Since this is inside the Class Projectile which extends from PVector, the line in questions is invoking the add() associated to PVector. This is a core concept in object oriented programming where your Projectile class is inheriting fields, functions defined in PVector.

In other words, you can think of that line as this.add(velocity); so it is adding velocity to the member variables x,y,z, associated to your instantiated Projectile object, variables inherited from the PVector class.

Kf

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3

Okay. Thank you. One more question too. Is it also the same idea with ellipse(x, y, 3, 3)? So the x and y are from PVector?

4

That is correct. You can see this in the docs and it the actual code:

Kf

1 Like