如何键入属性和值均来自其他类型的对象

Posted 2021-03-27

我想输入一个对象，其中属性值是仅允许为某种类型的数组，而其属性也仅允许为某种类型（联合类型）。我在下面尝试了两种不同的方法。带有Record的一种，它不允许我区分蔬菜和水果类型。还有不允许我将属性名称限制为某种类型的接口。

img of code

type Veg = 'corn' | 'broccoli' | 'onion' | 'pumpkin' | 'squash' | 'kale';
type Fruit = 'banana' | 'apple' | 'orange' | 'pineapple' | 'passionfruit';
type AllowedFood =  Veg | Fruit;
type AllowedFoodGroups = 'veg' | 'fruit';

// allows me to put the wrong food type (a fruit) in veg (the orange)
const DietShoppingList: Record<AllowedFoodGroups, AllowedFood[]> = {
    veg: ['corn', 'onion', 'orange'],
    fruit: ['banana']
}


interface DietShoppingList2{
    veg: Veg[],
    fruit: Fruit[]
}


// correctly identifies that orange doesn't belong to veg but lets meat exist or any other food
const DietShoppingList2: DietShoppingList2 = {
    veg: ['corn', 'onion', 'orange'],
    fruit: ['banana'],
    meat: ['fish']
}

答案

我为此here开枪了。看看让我知道您的想法。

type TBD<K, T> =
  & { [key: string]: never }
  & { [key: number]: never }
  & { [key in K & keyof T]: T[key] }

// correctly identifies that orange doesn't belong to veg & doesn't let meat any other food exist 
const dietShoppingList4: TBD<AllowedFoodGroups, DietShoppingList2> = {
    veg: ['corn', 'onion', 'orange'],
    fruit: ['banana'],
    meat: ['fish'],
    pulses: ['kidney bean', 'lima bean', 'lentil']
}

[与使用Record（即Object literal may only specify known properties, and 'meat' does not exist in type 'Record<AllowedFoodGroups, AllowedFood[]>'）时不会产生相同的错误，但是它确实满足了限制键和值同时将键保持为一种类型并允许不同的值类型的目标。

我对TypeScript和类型仍然很陌生，所以也许还有另一种方法可以对无效键给出更好的错误。