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7463 :: How to change teh default initialisation for object types

• halloleo (orginal) [2021-02-02T04:06:27+01:00] view original

  I have a "class" type like this:

  
  type
    Question = object
      what: string
      answer: int
  Run

  When I instantiate a Question object the default way I get

  
  $ echo Question()
  
  (what: "", answer: 0)
  Run

  How can I change the declaration to another default value for answer?

  I tried

  
  type
    Question = object
      what: string
      answer = 42
  Run

  But then the compiler complains with "Error: initialization not allowed here"

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• ElegantBeef (orginal) [2021-02-02T04:09:52+01:00] view original

  Nim currently does not have default values for constructors. You could use my package made for generating constructors to quickly make a proc that does as such.

  import constructor/construct
  
  type
    Question = object
      what: string
      answer: int
  Question.construct(true):
    answer = 42
  assert initQuestion() == Question(answer: 42)
  Run

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• halloleo (orginal) [2021-02-02T05:26:59+01:00] view original

  Your package looks super interesting! Thanks.

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• Stefan_Salewski (orginal) [2021-02-02T07:16:39+01:00] view original

  Without use of external packages we generally declare an init() proc for value objects like initMyObj() or a new proc like newButton() for a reference object, and we can pass arbitrary arguments for initialization to these procs.

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