Typescript

Question

我想键入一个键值相同的对象：

const myObj = {
    FOO: 'FOO',
    BAR: 'BAR'
};

我尝试使用 myObj 和 key:

设置 typeof

const actions: { [x: string]: x } = { // 'x' refers to a value, but is being used as a type here. Did you mean 'typeof x'?
    set: 'set1'
}

const actions: { [x: string]: typeof x } = {
    set: 'set1'  // doesn't trigger
}

const actions: { [p: string]: keyof typeof actions } = {
    set: 'set' // Type 'string' is not assignable to type 'never'.
}

type K = 'set' | 'set2';
const actions: { [p in K]: K } = { // triggers missing set2
    set: 'set1' // doesn't trigger
}

有没有办法确保键和值始终匹配？ TIA！

Answer 1

您可以通过创建一个辅助函数来实现这一点，该函数接受您的对象，然后通过生成额外的参数对其进行 TypeScript 检查，如果给定的对象没有通过我们相同的参数，这些参数将使您的代码失败 key/value法.

// basically, we create an extra parameter when the object is not valid
function createSamePairedObject<T extends Readonly<Record<PropertyKey, PropertyKey>>>(obj: T, ..._lockParams: T extends { [K in keyof T]: K } ? [] : ["INVALID_PAIRED_OBJECT"]): T {
  return obj as any;
}

// PASS
const a = createSamePairedObject({ // { readonly a: "a" }
  a: "a",
} as const);

// FAIL - "b" != "bb"
const b = createSamePairedObject({
  a: "a",
  b: "bb",
} as const);

// FAIL - not const object
const c = createSamePairedObject({
  [5]: 5,
});

// PASS
const d = createSamePairedObject({
  [5]: 5,
} as const);

TypeScript Playground Link

Answer 2

玩了一会儿搞定了：

type K = 'set' | 'set2';
const actions: { [p in K]: p } = { // note that I am using p instead of K from the question
    set: 'set1'
}

使用此设置我得到以下错误：

TS2741: Property 'set2' is missing in type '{ set: "set"; }' but required in type '{ set: "set"; set2: "set2"; }'.

TS2322: Type '"set1"' is not assignable to type '"set"'.

以下是让它开心的原因：

type K = 'set' | 'set2';
const actions: { [p in K]: p } = {
    set: 'set',
    set2: 'set2'
}

更新：如果您有已知的键列表，此方法有效，但如果您有未知的键列表或要将任何键与其值匹配，请遵循@sno2 的

Typescript - 如何使值等于对象的键？

Typescript - How to make values to equal the keys of an object?

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