Function exists for a "new" instance but not for a previously existing one?

Programming Questions

fernozzle

Function exists for a "new" instance but not for a previously existing one?

in Programming Questions • 4 months ago

I have a class, Point2d, and a function, drawPoint2d:

class Point2d {
  float x, y;
  Point2d (float x, float y) {
    this.x = x;
    this.y = y;
  }
}
void drawPoint2d (Point2d p) {
  ellipse (p.x, p.y, 10, 10);
}

And they seem to work fine:

void setup () {
  drawPoint2d (new Point2d (10, 10));
  //Point2d p = new Point2d (10, 10);
  //drowPoint2d (p);
}

However, if I were to uncomment the two commented lines, I'd receive an error message reading "The function drawPoint2d(AnExampleSketch.Point2d) does not exist.", with "AnExampleSketch" being the name of my sketch.

Why would this be? I'm using Processing 2.0, and I don't remember if I've encountered a similar error before.

Replies(2)

GoToLoop

Re: Function exists for a "new" instance but not for a previously existing one?

4 months ago

You have a mistype -> drowPoint2d(p);

Here's the fixed code. Although your example defeats OOP!

class Point2d {
  float x, y;
  Point2d (float x, float y) {
    this.x = x;
    this.y = y;
  }
}

void drawPoint2d(Point2d p) {
  ellipse(p.x, p.y, 10, 10);
}

void setup() {
  noLoop();
  
  drawPoint2d( new Point2d (10, 10) );
  
  Point2d p = new Point2d(30, 30);
  drawPoint2d(p);
}

GoToLoop

Re: Function exists for a "new" instance but not for a previously existing one?

4 months ago

An example where the class itself contains the methods which use its own member variables:

final class Point2d {
  int x, y;
  static final byte DIM = 10;

  Point2d(int xx, int yy) {
    x = xx;
    y = yy;
  }

  void displayCircle() {
    ellipse(x, y, DIM, DIM);
  }

  void displaySizedCircle(int dim) {
    ellipse(x, y, dim, dim);
  }
}

void setup() {
  noLoop();
  background(-1);

  final Point2d c1 = new Point2d(10, 10);
  final Point2d c2 = new Point2d(width - 10, height - 10);

  fill(#00FF00);
  c1.displayCircle();
  c2.displayCircle();

  c2.x = width  >> 1;
  c2.y = height >> 1;

  fill(#FFFF00);
  c2.displaySizedCircle(50);
}

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