Js immutable - 如何将地图展平为 Set<number>

Question

我有一个 Map<number, Shipment> 类型的货件，货件有一个属性 packageIds 类型 Set<number>。当我有多批货物时，我想检查每批货物，得到他们的 packageIds 并用每批货物的所有 packageIds 制作一个新的平面集：

shipments.flatMap(shipment => shipment.get('packageIds'))

但是，如果我这样做，我会收到打字稿错误：

TS2322: Type 'Set<number>' is not assignable to type 'Iterable<[unknown, unknown]>'.
  The types returned by '[Symbol.iterator]().next(...)' are incompatible between these types. 
  Type 'IteratorResult<number, any>' is not assignable to type 'IteratorResult<[unknown, unknown], any>'.       
  Type 'IteratorYieldResult<number>' is not assignable to type 'IteratorResult<[unknown, unknown], any>'.         
  Type 'IteratorYieldResult<number>' is not assignable to type 'IteratorYieldResult<[unknown, unknown]>'.           
  Type 'number' is not assignable to type '[unknown, unknown]'.

如何在遍历地图时获得平面集？

Answer 1

之前的immutablejs flatMap method of Maps returns another Map. That's not what you want. Convert to a Set，丢弃了Map键：

shipments.toSet().flatMap(shipment => shipment.get('packageIds'))

Js immutable - 如何将地图展平为 Set<number>

Js immutable - how to flatten a map to a Set<number>

javascript

typescript

immutable.js