Mobx observable deep object

Question

I looking for best solution how to implement @observable on deep json object structure (for example a tree) data tree could be go really deep. and each node has many properties, but I need to observe only one property in tree node. Simply if I do

@observable questionnaire = {}

it works, but i think that is waist. I need observe only 'selected' property. Here is json structure. Please correct me if i'm wrong here is questionnaire object simplified.

[
  {
    "id": "1",
    "title": "level 1",
    "description": "text",
    "type": "Question",
    "selected": false,
    "childNodes": [
      {
        "title": "level 2",
        "description": "text",
        "type": "Question",
        "selected": false,
        "childNodes": [
          {
            "title": "level 3",
            "description": null,
            "type": "Question",
            "selected": false,
            "childNodes": [
              {
                "title": "level 4 1",
                "childNodes": [],
                "description": null,
                "type": "Checkbox",
                "selected": false
              },
              {
                "title": "level 4 2",
                "childNodes": [],
                "description": null,
                "type": "Checkbox",
                "selected": false
              },
              {
                "title": "level 4 3",
                "childNodes": [],
                "description": null,
                "type": "Checkbox",
                "selected": false
              },
              ...
            ]
          }, ...

Answer 1

One way is to have a Node class implemented as follows:

class Node {
  @observable selected = false;
  @observable childNodes = asFlat([]);

  constructor(data) {
    // Recursively create `Node` objects for all children.
    data.childNodes = data.childNodes.map(child => new Node(child));
    Object.assign(this, data);
  }
}

Then you create a Node object from your top-level json object: new Node(json) .

This solution will only observe selected and childNodes . It's not ideal because you need to wrap your json object in Node objects. But I can't think of any other way to do it.