9.5 Methods with Arguments and Result

One last possibility is the combination of arguments with a result. One common pitfall: although a method can have many arguments, it can only have one result.

The next example implements a move method. This method will move a circle by passing a value as an argument. This value will be added to the currrent position, but only as long as the result would not be outside of the screen. By returning a bool as a result, we can let the application know if movement succeeded.

 
class movingCircle { 
  Circle c    ; 
  Vec2   speed; 
 
5  void init(float r, Vec2 pos, Vec2 speed) { 
    c.r         = r    ; 
    c.pos       = pos  ; 
    this->speed = speed; 
  } 
10 
  float getRadius() { 
    return c.r; 
  } 
 
15  bool move(Vec2 pos) { 
    if(Cuts(c.pos + pos, D.viewRect())) { 
      c.pos += pos; 
      return true; 
    } else { 
20      return false; 
    } 
  } 
} 
 
25// somewhere in your application 
movingCircle mc; 
Vec2 p(0, 0); 
mc.init(0.1, p, Vec2(0.3, -0.5)); 
if( !mc.move(mc.speed * Time.d()) ) { 
30  // do something when failed 
}