Mirror of forum.nim-lang.org

6038 :: Exporting the tostring procedure along with a type

• abhijat0 (orginal) [2020-03-05T16:10:07+01:00] view original

  I have a program with the following components:

  • a main.nim file, a utils.nim file and story.nim
  • story.nim defines a type Story and also its tostring procedure. A proc in utils returns the story object. main calls the proc to get the story and prints it.
  • I need to import story in utils but not in main, as due to type inference I do not need to actually specify story type anywhere in main.

  If I echo my story type in main, the tostring used is the default one for a type, and not the one I defined.

  If I import story in main, then my tostring is used.

  main.nim

  import utils
  
  let story = parseStory(...)
  echo(story) # this prints the default object string. if I import story in this file, then the custom tostring is used.
  Run

  utils.nim

  import story
  
  proc parseStory*(filename: string): Story =
    ...
  Run

  story.nim

  type
    Story* = object
      ...
  
  proc `$`*(s: Story): string =
    ....
  Run

  Is there a way to print story with the custom representation I defined without importing it in main, by binding it with the type somehow?

---

• DeletedUser (orginal) [2020-03-05T16:25:55+01:00] view original

  I think "tying procedures to objects" is a planned compiler behaviour for the future, but I think the accepted behaviour currently is doing import story in this case. If you come across this situation where you specifically need utils but not story more than once, you can do this:

  # utils.nim
  import story
  export story.`$`
  
  proc parseStory*(filename: string): Story =
    ...
  Run

---

• abhijat0 (orginal) [2020-03-05T17:49:34+01:00] view original

  Thanks, exporting seems to be a good way to do this, did not know about that.

---