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7919 :: How to map a JS dictionary paramter in the Nim importjs header?

• halloleo (orginal) [2021-05-04T09:34:48+02:00] view original

  I have a JavaScript library with a function which takes a dictionary object as parameter:

  
  function myfunc(data, opts) {
      ...
      //opts is used like:
     opts.type == ...
     opts.desc ...
      ...
  }
  Run

  In the Nim header definition like

  
  func myfunc*(data: cstring, opts: ???) {.importjs: "mylib.$1(#, #)".}
  Run

  I can map data to cstring, but what do I map opts to?

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• DomoSokrat (orginal) [2021-05-04T09:54:26+02:00] view original

  Try JsObject or JsAssoc from the jsffi stdlib module.

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• halloleo (orginal) [2021-05-04T10:26:53+02:00] view original

  Cool! Makes sense. Now I'm using:

  
  func myfunc*(data: cstring, opts: JsObject) {.importjs: "mylib.$1(#, #)".}
  Run

  And I'm trying on the Nim side to provide this` JsObject` aka dictionary:

  
  let opts = toJS({"type": "extended", "desc": "fortified"}.totable)
  myFunc(data, opts)
  Run

  This compiles and runs, but on the JavaScript side opts.type is undefined and not as I hoped/expected "extended".

  Any idea how to write the JsObject dictionary in Nim correctly?

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• DeletedUser (orginal) [2021-05-04T12:32:20+02:00] view original

  You should do js{"type": "extended", "desc": "fortified"} using the {} macro. Tables can only have a single type for values, {"a": "foo", "b": 1}.toTable does not compile. Also they are a pure Nim type

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• DomoSokrat (orginal) [2021-05-04T13:49:05+02:00] view original

  I would have expected that to do the right thing…

  As it turns out, you can use the macro {}, but then you can't use variables as keys:

  let opts = JsObject{`type`: cstring"extended", desc: cstring"fortified"}
  Run

  Or set the fields explicitly:

  var opts = newJsObject()
  opts["type"] = cstring"extended"
  opts["desc"] = cstring"fortified"
  Run

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• halloleo (orginal) [2021-05-05T11:57:10+02:00] view original

  @DomoSokrat @Hlaaftana Thanks a lot for the info. I guess I have to study jsffi in more detail…

  (Still, discovery of unknown syntax doesn’t seem to be easy for me just from the type/function reference line on the module page.)

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