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4810 :: ObjectAssigmentError

• DavidM (orginal) [2019-04-26T00:27:37+02:00] view original

  Trying to compile this but I get an ObjectAssigmentError when the items array is assigned.

  I want to use B and C for common behavior. What am I doing wrong?

  type
    A = object of RootObj
      name: string
    B = object of A
      value: string
    C = object of A
      key: int
  
  let items : seq[A] = @[
    B(name:"Test", value:"Value"),
    C(name:"Test", key:100)
  ];
  
  
  
  

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• miran (orginal) [2019-04-26T07:22:23+02:00] view original

  What am I doing wrong?

  You're not using ref object:

  type
    A = ref object of RootObj
      name: string
    B = ref object of A
      value: string
    C = ref object of A
      key: int
  Run

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• Stefan_Salewski (orginal) [2019-04-26T08:00:42+02:00] view original

  Adding some more details to mirams answer: You are trying to put value objects of different type and size into the same seq. But for seq and array all elements must have the same size. With ref that works, because ref is basically a pointer, and all have the same size. You may also consider sum types/object variants instead of your OOP like design.

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• mratsim (orginal) [2019-04-26T10:17:34+02:00] view original

  We probably could use a better error message on inherited stack object, or prevent them altogether if fields do not have the same types.

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