javascript - 基于key的流对象值

Question

当使用流程时，我一直想输入这样的内容:

type Item = {
  timestamp: number,
  status: { completed: boolean },
  data: string,
}

type Filter = {
  timestamp: number,
  status: { completed: boolean },
}

const FilterFns: {
  [key: $Keys<Filter>]: ($ElementType<Filter, key>, item: Item) => boolean
} = {
  timestamp: (timestamp, item) => timestamp === item.timestamp,
  status: (status, item) => status.completed === item.status.completed,
}

但我收到错误:

13:   [key: $Keys<Filter>]: ($ElementType<Filter, key>, item: Item) => boolean
                                                  ^ Cannot resolve name `key`.

如果我将 FilterFns 定义为:

const FilterFns: {
  [key: $Keys<Filter>]: ($Values<Filter>, item: Item) => boolean
} = {
  timestamp: (timestamp, item) => timestamp === item.timestamp,
  status: (status, item) => status.completed === item.status.completed,
}

我收到错误:

16:   status: (status, item) => status.completed === item.status.completed,
                                       ^ Cannot get `status.completed` because property `completed` is missing in `Number` [1].
References:
8:   timestamp: number,
                ^ [1]

确保传入函数的 FilterFns 值中的第一个参数是 Filter 中对应类型的正确方法是什么？

Answer 1

不是对象键问题的通用解决方案，但可以通过下一种方式解决特定情况

type Item = {
  timestamp: number,
  status: { completed: boolean },
  data: string,
}

type Filter = {
  timestamp: number,
  status: { completed: boolean },
}

const FilterFns: {
  [key: $Keys<Filter>]: ($Values<Filter>, item: Item) => boolean
} = {
  timestamp: (timestamp, item) => timestamp === item.timestamp,
  status: (status, item) => typeof status === 'object' && status.completed === item.status.completed,
}

添加附加条件typeof status === 'object'将允许流程识别现在的确切值，否则不幸的是，流程无法获得正确的键对-值