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9568 :: How to use multi-type parameters in the Nim

• winger (orginal) [2022-11-02T09:11:11+01:00] view original

   test(domains:(string|seq[string])) =
      var domainseq:seq[string]
      if typeof(domains) is string:
          domainseq = @[domains]
      else:
          domainseq = @["abc"]
      echo domainseq
  
  test(@["xxx.com"])
  Run

  Error: type mismatch: got 'seq[seq[string]]' for '@[domains]' but expected 'seq[string]'

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• Stefan_Salewski (orginal) [2022-11-02T10:52:03+01:00] view original

  Nim is a statically typed language. So an instantiated proc has always well defined paramter types. What you can do, is to test with when which kind of proc was actually created by the compiler for the actual parameter. Replace your if test with when, like "when typeof(domains) is string:"

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• Araq (orginal) [2022-11-02T14:54:26+01:00] view original

  proc test(domains: seq[string]) = # 1
    echo domains
  
  proc test(domain: string) = test(@[domain]) # 2
  
  test @["xxx.com"] # calls 1
  test "yyy.com" # calls 2
  Run

  You can use overloading here. But it is a bad idea for a beginner. If you deal with a list of domains, offer the seq[string] variant and use that.

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• winger (orginal) [2022-11-03T03:10:08+01:00] view original

  thanks

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• winger (orginal) [2022-11-03T03:10:44+01:00] view original

  It's a wise move. Tanks

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