Question

使用Mobx，我尝试按照future.cancel(true);中scheduleTaskExecutor.shutdown();的顺序输出booksByIdMap中的图书标题：

booksSortedIdArray

class BookStore { @observable booksSortedIdArray = ["88cd7621", "88cd7624", "88cd7623", "88cd7622"]; @observable booksByIdMap = asMap({ "88cd7621": { "id": "88cd7621", "title": "The Secret" }, "88cd7622": { "id": "88cd7622", "title": "The Alchemist" }, "88cd7623": { "id": "88cd7623", "title": "Javascript" }, "88cd7624": { "id": "88cd7624", "title": "PHP" } }); @computed get byBookId() { return this.booksByIdMap.values().filter(b => this.booksSortedIdArray.includes(b.id)); } }中的filter似乎没有维持该排序顺序而是输出：

byBookId

而不是：

The Secret, The Alchemist, Javascript, PHP

这是fiddle。

如何根据The Secret, PHP, Javascript, The Alchemist中的ID排序顺序输出标题？

Answer 1

您可以在数组上使用reduce，并尝试从地图中get每个键。如果存在，只需将其添加到结果中即可。 This way you will get it in order：

class BookStore {
  @observable booksSortedIdArray = ["88cd7621", "88cd7624", "88cd7623", "88cd7622"];
  @observable booksByIdMap = asMap({
    "88cd7621": {
      "id": "88cd7621",
      "title": "The Secret"
    },
    "88cd7622": {
      "id": "88cd7622",
      "title": "The Alchemist"
    },
    "88cd7623": {
      "id": "88cd7623",
      "title": "Javascript"
    },
    "88cd7624": {
      "id": "88cd7624",
      "title": "PHP"
    }
  });

  @computed get byBookId() {
    return this.booksSortedIdArray.reduce((res, el) => {
      const book = this.booksByIdMap.get(el);
      if(book) {
        res.push(book);
      }
      return res;
    }, []);
  }
}

过滤asMap计算值维护排序顺序？

1 个答案: