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8813 :: closure and for loop problem

• Aquachain (orginal) [2022-01-16T17:27:57+01:00] view original

  Hello Nim friends!

  i dont known how i can solve this problem. See minimal and runnable example:

  type
    Foo = object
      something: proc()
  
  var
    foos: seq[Foo]
  
  # test 1 does not work because of closures
  # for i in 1..10:
  #   var f: Foo
  #   f.something = proc() = echo $i
  #   foos.add(f)
  
  # test 2 also does not work and i dont know why.
  for i in 1..10:
    let j = i
    var f: Foo
    f.something = proc() = echo $j
    foos.add(f)
  
  for f in foos:
    f.something()
  Run

  in Javascript and in C# i can simply copy the variable (like in test2), but i miss something. I use the current dev version of Nim 1.7.1 on Windows 10.

  Can you help me?

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• aEverr (orginal) [2022-01-16T17:31:19+01:00] view original

  needs closure scope capture https://nim-lang.org/docs/system.html#closureScope.t%2Cuntyped

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• Aquachain (orginal) [2022-01-16T17:34:36+01:00] view original

  Thank you very much! I didnt know about this.

  For other readers this is the solution:

  for i in 1..10:
    closureScope:
      let j = i
      var f: Foo
      f.something = proc() = echo $j
      foos.add(f)
  Run

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