objects call objects?

strinda

Hi, I have an object (say a tank) and it calls another objects as its part, say, a turret. Now, I need the turret object to quer the tank object and ask for its coordinates and I can't get whether it can be done at all.

This is my code:

class Tank {

constructor () {
this.location = createVector (windowWidth/2, windowHeight/2)
this.velocity = createVector (0,-2);

this.sizeW = 50;
this.sizeH = 100;
this.angle = 0;

this.turret1 = new Turret;
}

show () {

push ();
translate (this.location.x, this.location.y);
rotate (radians(this.angle));
rectMode (CENTER);
rect (0, 0, this.sizeW, this.sizeH);
pop();

this.turret1.show();
}   

rot (angle) {
this.angle = this.angle + angle;
this.velocity.rotate (radians(angle)); 
println (this.angle);
}

moveForward () {
this.location.add(this.velocity);
}

getLocation () {
return this.location}
}


class Turret {
constructor () {
this.location = createVector (windowWidth/2, windowHeight/2);
}

// This method needs to talk to the Tank //
update () {
this.location = this.Tank.getLocation();
}


show () {
//update();
ellipse (this.location.x,this.location.y, 50,50);
}

}

TfGuy44

You shouldn't do it that way.

Each class (and thus, each object) you write should be a self-contained thing. That is, if you have a tank that has many turrets, the turrets themselves should not need to ask the tank they are on anything, because this creates a dependent relationship between the turret and the tank, which means the turret is not self-contained.

What you can do, instead, is have the tank tell the turrets to be in a new location. The turrets can they do whatever a turret likes with that information (like update its location (or not! maybe your tank has dropped a stationary turret, and the turret itself knows that it is stationary!)).

Something like this:

class Tank {

  constructor () {
    this.location = createVector (windowWidth/2, windowHeight/2)
    this.velocity = createVector (0, -2);
    this.sizeW = 50;
    this.sizeH = 100;
    this.angle = 0;
    this.turret1 = new Turret;
  }

  show () {
    push ();
    translate (this.location.x, this.location.y);
    rotate (radians(this.angle));
    rectMode (CENTER);
    rect (0, 0, this.sizeW, this.sizeH);
    pop();
    // Here the turret is told to use a new location by the tank.
    this.turret1.update(this.location);
    this.turret1.show();
  }   

  rot (angle) {
    this.angle = this.angle + angle;
    this.velocity.rotate (radians(angle)); 
    println (this.angle);
  }

  moveForward () {
    this.location.add(this.velocity);
  }

  getLocation () {
    return this.location
  }
}


class Turret {
  constructor () {
    this.location = createVector (windowWidth/2, windowHeight/2);
  }

  update (new_location) {
    // This turret moves because the tank told it to.
    this.location = new_location;
  }

  show () {
    ellipse (this.location.x, this.location.y, 50, 50);
  }
}

strinda

thank you, everything is clear.