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6372 :: Playing with objects - object referecing another object

• mantielero (orginal) [2020-05-23T20:24:58+02:00] view original

  I have not used OOP in Nim so far. I was playing with the following code:

  type
    Coord = ref object of RootObj
      x,y,z:float
    
    Pt* = ref object of Coord
    
    Tmp = ref object of RootObj
      tag:int
      point:ref Pt
  
  
  let a =  Pt(x:1.0, y:3.0,z:2.0)
  
  let d = Tmp(tag: 4, point: a )    #<<<< This is what I am interested in
  echo repr d
  Run

  where I got:

  /tmp/ex01.nim(14, 26) Error: type mismatch: got <Pt> but expected 'ref Pt'

  How do I pass a reference?

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• mantielero (orginal) [2020-05-23T20:40:00+02:00] view original

  I think I just had to remove the ref in Tmp definition:

  type
    Coord = ref object of RootObj
      x,y,z:float
    
    Pt* = ref object of Coord
    
    Tmp = ref object of RootObj
      tag:int
      point:Pt
  
  
  let a =  Pt(x:1.0, y:3.0,z:2.0)
  let b = a
  echo repr b
  
  et d = Tmp(tag: 4, point: b )
  echo repr d
  d.point.x = 2.0
  echo repr d
  echo repr b
  Run

  This seems to work.

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• Yardanico (orginal) [2020-05-23T21:08:04+02:00] view original

  Yeah, because otherwise it would've been "ref Pt" which means "ref to ref to object of Coord".

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