Functions / vectors

Comments

• Ignatz Mod

  October 2014 edited October 2014 Posts: 5,396

  Alex

  you should only use "self" inside a class. This should work..

  function limit (v, max)
      if v:len() > max then return v:normalize() * max
      else return v  
      end   
  end
  

  PS you were also missing an end statement after your if
• alexNaumov

  October 2014 Posts: 25

  Thank you very much. I read your post about the "self" word, but I am still struggling with it)
• Ignatz Mod

  October 2014 Posts: 5,396

  The code in a class is used by all the objects you create with that class.

  If, for example, the class has a position property, that will be different for all the objects you create with that class, then you need some way of storing position separately for each object, and being able to find it later.

  Self does that. It simply means "whichever object is using the code at the moment", and I think of it visually, as being like a room full of lockers, where each locker holds information for an object in the class, and self is the name on the locker.

  So you might give instructions like "when people come into the locker room, get their id number, ID, and make them put their clothes in the locker labelled ID".

  In the same way I used ID as a placeholder for whatever the id number is, "self" is just a placeholder. It tells Codea to replace it with the address of the data for the current object using the code.
• alexNaumov

  October 2014 Posts: 25

  Why would this function not work?

  It is intended to return the pod vector, which I will be using in the main tab

  function Unit:pos()
  return self.pos
  end
• Ignatz Mod

  October 2014 Posts: 5,396

  Maybe you are calling it incorrectly

  a=Unit()
  b=a.pos()  --incorrect, uses full stop
  b=a:pos()  --correct, uses colon
  
• alexNaumov

  October 2014 Posts: 25

  The problem lies somewhere in this line:
  print(spacecraft[3]:pos())

  I have previously initialized each object in he table.
• Ignatz Mod

  October 2014 Posts: 5,396

  That code looks all right, you'll need to post more code
• alexNaumov

  October 2014 Posts: 25

  I will, thank you for your feedback.
• alexNaumov

  October 2014 Posts: 25

  function setup()
  number = 20
  spacecraft = {}
  
  
      for i = 1, number do
      table.insert (spacecraft, Unit (math.random(100,200), math.random(200,300), math.random (1,8)))
      print(spacecraft[i]:pos())
  end
  end
  
  
  function draw()
  
  background(40, 40, 50)
  
   for i = 1, 20 do
      spacecraft[i]:script()
   end
   end
  

  And the function itself

  function Unit:pos()
  return self.pos
  end
  
• Ignatz Mod

  October 2014 edited October 2014 Posts: 5,396

  @alexNaumov - this is an interesting problem.

  I think you may find it works if you change the pos function name in the Unit class, to something else, eg position. That worked for me.

  The reason, I think, is that self.pos can refer to both the function Unit:pos and the class variable self.pos, so you need to have different names.

  When you call spacecraft[i]:pos(), Codea actually calls spacecraft[i].pos(self), then it finds that self.pos is a vec2 and causes an error.
• JakAttak

  October 2014 Posts: 2,051

  You can't have a function named the same as your variable

  You could use metatables to make it so that what you are doing works, or you could just rename one of them