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6153 :: Complex types serialization

• readysloth (orginal) [2020-04-04T18:11:51+02:00] view original

  Hi all

  I defined my own type, lets name it A, and created table :

  var dictionary = new_table[A, Hash_set[A]]()
  Run

  Now i want serialize this data, but failed to do this, currently. I tried json module, but, as spec says, Json cant represent complex types as keys in dictionaries. So I felt back on marshal module, which, actually, creates json from my table, but when I try compile code with deserialization:

  var unmarshalled = read_file("marshalled.json").to[typeof(dictionary)]
  Run

  it throws

  
  /lib/marshal.nim(317,10) Error: cannot instantiate : 'T'
  Run

  What can i do, to serialize this structure?

  My nim compiler version is 1.0.6

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• DeletedUser (orginal) [2020-04-04T20:45:38+02:00] view original

  You have to do .to[:typeof(dictionary)], the colon after the [ indicates that it is supplying generic arguments instead of doing array subscript access. The last paragraph here is reference: https://nim-lang.org/docs/manual.html#procedures-method-call-syntax

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• readysloth (orginal) [2020-04-06T14:35:22+02:00] view original

  Thank you for the answer, it works! But deserialization throws runtime exception :(

  /usr/lib/nim/pure/marshal.nim (333) to
  /usr/lib/nim/pure/marshal.nim (266) loadAny
  /usr/lib/nim/pure/marshal.nim (179) loadAny
  /usr/lib/nim/pure/parsejson.nim (522) raiseParseErr
  Error: unhandled exception: unknown file(1,1) Error: '{' expected for an object expected [JsonParsingError]
  Run

  But why?... '{' in place

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