问无法将数据从fetch调用推送到mobx可观察对象数组中

EN

//need fetch response in here
let model = observable({
  Ratings: [],
  Instructors: [],
  Likes: [],
  Schools: []
});

export let Model = toJS(model);

Model.Fetch = async function() {
  const endPoint = "http://s28.ca/sodv2201/instructor/ratings";
  const req = {};

  let P = await fetch(endPoint, {
    method: "POST",
    body: JSON.stringify(req)
  });
  let data = await P.json();

  //the object I need(goes deeper, ex. data.Ratings.Ratings,
  //data.Ratings.Instructors)
  let ratings = data.Ratings;
  //doesn't work
  model.Ratings = ratings.Ratings;

  //model appears to be right, but fails when
  //adding to Model, can see arrays, no data in them
  model = ratings;
  console.log(model);