流程-具有联合类型的交叉点错误:“无法在任何交叉点类型的成员上访问属性" [英] Flow - intersection with union types error: "Property cannot be accessed on any member of intersection type"

问题描述

代码可以尝试此处

我的类型是联合类型的交集:

I have a type that is an intersection of union types:

type Location = {
  latitude: number,
  longitude: number
} & ({
  locationType: 'country',
  country: string
} | {
  locationType: 'state',
  state:string
})

我还有另一个函数，该函数根据联合类型之一进行操作:

I have another function that does something based on one of the union types:

const getLocationValue = (location: Location): string => {
  if (location.locationType === 'country')
    return location.country
  else
    return location.state
}

但是，这给了我错误:

属性country.无法在路口类型的任何成员上访问属性

property country. Property cannot be accessed on any member of intersection type

^属性state.无法在路口类型的任何成员上访问属性

^ property state. Property cannot be accessed on any member of intersection type

Flow应该能够理解，如果locationType是country，那么它应该具有country属性.

Flow should be able to understand that if locationType is country, then it should have a country property.

我在做什么错了?

推荐答案

为了使用不相交联合流需要2种以上的类型可供选择.当前，您仅定义了一种类型:Location.您可以将公用值划分为一种抽象"类型，并使Location为真正的类型并集，以使Flow可以在它们之间进行选择.看起来可能如下所示:

In order to use a disjoint union Flow needs 2+ types between which to choose. Currently you have defined only a single type: Location. You can split the common values into a sort of "abstract" type and make Location a true type union in order to enable Flow to choose between them. It could look like the following:

type AbstractLocation = {
  latitude: number,
  longitude: number,
}

type CountryLocation = AbstractLocation & {
  country: string,
  locationType: 'country',
}

type StateLocation = AbstractLocation & {
  locationType: 'state',
  state: string,
}

type Location = CountryLocation | StateLocation

尝试:上flow.org工作示例

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