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收到错误后，unions can't be used in index signatures, use a mapped object type instead我现在尝试将字符串文字联合（接口的键名）转换为映射对象，如此处所述。https://github.com/microsoft/TypeScript/issues/24220#issuecomment-390063153

但它仍然无法正常工作：

const returnObject: { 
   [index : mappedObjectOfConfigDataKeys] : Partial<ConfigData>
 } = {...accumulator};

// error TS1023: An index signature parameter type must be either 'string' or 'number'.

// 51 [index : // mappedObjectOfConfigDataKeys] : // Partial<ConfigData>
//     ~~~~~


 if (currentStepInstance.hasSaveableData && currentStepInstance.configDataKey) {
    returnObject[currentStepInstance.configDataKey] = validatedUserInput;
 } 
// error TS7053: Element implicitly has an 'any' type because expression of type 'string' can't be used to index type '{}'.
//  No index signature with a parameter of type 'string' was found on type '{}'.

// 55  returnObject[currentStepInstance.configDataKey] = validatedUserInput;
       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

为了证明前面的问题：

const returnObject: { 
   [index : stringLiteralUnion] : Partial<ConfigData>
 } = {...accumulator};

// (parameter) index: stringLiteralUnion
// An index signature parameter type cannot be a union type. Consider using a mapped object type instead.ts(1337)

有人知道怎么修这个东西吗？这最后两次尝试让我陷入了困境。编译器似乎希望映射对象传递一组受约束的字符串；我不知道如何以可接受的方式给予它。

export default interface ConfigData {
   languageCode : string
   , numberOfRepeats : number
   , projectId : string
}

/**** Index Signature handling for the above interface ****/
export type stringLiteralUnion = "languageCode" | "numberOfRepeats" | "projectId";

export type mappedObjectOfConfigDataKeys = {[key in stringLiteralUnion]: string}; 
// also tried typing it as `any` as shown in the linked post
// same error occured

打字稿游乐场

链接到 TS Playground

更新 1

尝试：

const returnObject: Record<keyof ConfigData, Partial<ConfigData>> = {...accumulator};

错误信息：

const returnObject: Record<"languageCode" | "numberOfRepeats" | "projectId", Partial<ConfigData>>

Type '{ languageCode?: string | undefined; numberOfRepeats?: number | undefined; projectId?: string | undefined; }' is not assignable to type 'Record<"languageCode" | "numberOfRepeats" | "projectId", Partial<ConfigData>>'.

  Types of property 'languageCode' are incompatible.
    Type 'string | undefined' is not assignable to type 'Partial<ConfigData>'.
      Type 'undefined' is not assignable to type 'Partial<ConfigData>'.ts(2322)

更新 2

尝试：

const returnObject: Record<"languageCode" | "numberOfRepeats" | "projectId", Partial<ConfigData>> = {...accumulator};

错误：

const returnObject: Record<"languageCode" | "numberOfRepeats" | "projectId", Partial<ConfigData>>

Type '{ languageCode?: string | undefined; numberOfRepeats?: number | undefined; projectId?: string | undefined; }' is not assignable to type 'Record<"languageCode" | "numberOfRepeats" | "projectId", Partial<ConfigData>>'.

  Types of property 'languageCode' are incompatible.
    Type 'string | undefined' is not assignable to type 'Partial<ConfigData>'.
      Type 'undefined' is not assignable to type 'Partial<ConfigData>'.ts(2322)
4

2 回答 2

0

不确定您要达到的目标：

const returnObject: Record<keyof ConfigData, Partial<ConfigData>> = {...accumulator};
于 2020-07-04T12:47:48.530 回答
0

我需要将值转换为映射类型，而不是将索引签名键入映射对象。

这一行：

const returnObject: { 
   [index : mappedObjectOfConfigDataKeys] : Partial<ConfigData>
 } = {...accumulator};

变成这样：

const returnObject: Partial<ConfigData> = accumulator;
于 2020-07-04T17:29:14.577 回答