Various subclasses instanciated in an Arraylist?

luxregina

Hello! I'm relatively new to Processing and OOP.

I'm currently developing a shoot'em'up and I'm using Arraylists to 'control' my enemies. So far, everything has been working fine. I'm starting to get problems when I try to mix different sub-classes in the same arraylist. I can access the methods of all my childs, but I keep getting the fields of my parent.

I've done a fair amount of research, but without success: for clarity's sake, instead of posting my code that is quite lengthy, here's an example of what I'm trying to achieve:

ArrayList shapes = new ArrayList();
 
void setup() {
  shapes.add(new Rect());
  shapes.add(new Circle());
 
  for(Shape s : shapes) {
    if(s instanceof Rect) {
      println("type is rect");
      s.show();
      println("my ID is: "+s.ID);
    } 
    else if (s instanceof Circle) {
      println("type is circle");
      s.display();
      println("my ID is: "+s.ID);
    }
  }
}
 
 
class Rect extends Shape {
  String ID="I'm a rectangle";
  void show(){
   rect(5,5,10,10); 
  }
}
 
class Circle extends Shape {
  String ID="I'm a circle";
  void display(){
   ellipseMode(CORNER);
    ellipse(20,5,10,10); 
  }
}
 
class Shape {
  String ID="I'm nothing";
  void display(){};
  void show(){};
}

So, 2 questions:

1) how can I access the ID value of my subclass? I keep reaching for its parent value? I'm obviously missing something important... 2) I've read that using 'instanceof' is a bad bad thing: can someone explain why, and what I should do instead?

Thanks by advance!

Ater

The above code gives me ID's of subclasses:

type is rect
my ID is: I'm a rectangle
type is circle
my ID is: I'm a circle

The parent ID should be accessed with println("my ID is: "+s.super.ID);. Or didn't I get your question?

GoToLoop

https://forum.Processing.org/two/discussion/13616/inheritance-in-a-class-with-an-array-loop

luxregina

Alter: the code I posted shouldn't work - I've asked around and realized that my ID redefinition was local to my class...the proper way (that works) is

class Rect extends Shape {
  Rect (){
   ID="I'm a rectangle"; 
  }
  void show(){
   rect(5,5,10,10); 
  }
}

GotToLoop: thanks, awesome link - this is very close to what I'm attempting!