英文:
Why Record type in TS with undefined as a value should have strictly defined fields?
问题
以下是您要翻译的内容：
实际上，我的问题与下面的情况相关：我有一个用于表单值的类型```typescriptinterface FormValues {name: stringdescription: stringexpirationDate: Date | null}
以及一个用于在表单中存在错误时可以创建错误的类型
const errors: Record<keyof FormValues, string | undefined> = {name: undefined,description: undefined,expirationDate: undefined}
然而，只有在我将每个字段定义为undefined时，错误类型才起作用，如果我尝试将其更改为空对象，那么TypeScript会返回错误
const errors: Record<keyof FormValues, string | undefined> = {}/*Type '{}' is missing the following propertiesfrom type 'Record<keyof FormValues, string | undefined>': name, description, expirationDate*/
如何更改错误类型以反映我的需求，即将字段定义为字符串或不存在的对象：
const validate = values => {const errors: ??? = {}if (!values.name) errors.name = 'Required'if (!values.description) errors.description = 'Required'if (!values.expirationDate) errors.expirationDate = 'Required'return errors}
英文:
Practically my question is related to a situation below:
I have a type for form values
interface FormValues {name: stringdescription: stringexpirationDate: Date | null}
and a type for errors that can be created if there are errors in a form
const errors: Record<keyof FormValues, string | undefined> = {name: undefined,description: undefined,expirationDate: undefined}
however, the errors type works only if I define each fields as undefined, if I try to change it to an empty object, then TS responses with an error
const errors: Record<keyof FormValues, string | undefined> = {}/*Type '{}' is missing the following propertiesfrom type 'Record<keyof FormValues, string | undefined>': name, description, expirationDate*/
how to change the error type to reflect my need in having an object with the fields defined as a string or non-exist:
const validate = values => {const errors: ??? = {}if (!values.name) errors.name = 'Required'if (!values.description) errors.description = 'Required'if (!values.expirationDate) errors.expirationDate = 'Required'return errors}
答案1
得分: 1
请看这个（你的类型）：
type errorType1 = Record<keyof FormValues, string | undefined>;
等同于
type errorType1 = {name: string | undefined;description: string | undefined;expirationDate: string | undefined;}
然后看看
type errorType2 = Partial<Record<keyof FormValues, string>>;
等同于
type errorType2 = {name?: string | undefined;description?: string | undefined;expirationDate?: string | undefined;}
使用错误类型2，您可以忘记键。但使用第一个类型则不行。
您可能需要的是：
const errors: Partial<Record<keyof FormValues, string>> = {}
英文:
Take a look at this (your type) :
type errorType1 = Record<keyof FormValues, string | undefined>
wich is equivalent to
type errorType1 = {name: string | undefined;description: string | undefined;expirationDate: string | undefined;}
Then look at
type errorType2 = Partial<Record<keyof FormValues, string>>
which is equivalent to
type errorType2 = {name?: string | undefined;description?: string | undefined;expirationDate?: string | undefined;}
With error type 2, you are allowed to forget keys. With the first you can't.
What you need is probably :
const errors: Partial<Record<keyof FormValues, string>> = {}
答案2
得分: 1
您可以使用类型实用程序Partial<Type>来使类型的键变为可选的：
const errors: Partial<Record<keyof FormValues, string>> = {};
以下是一个完整的示例，基于您问题中的代码：
const formValueKeys = ["name","description","expirationDate",] as const satisfies readonly (keyof FormValues)[];const validate = (values: FormValues) => {const errors: Partial<Record<keyof FormValues, string>> = {};for (const key of formValueKeys) {if (!values[key]) errors[key] = "Required";}return errors;};
英文:
You can use the type utility Partial<Type> to make the keys of a type optional:
const errors: Partial<Record<keyof FormValues, string>> = {};
Here's a complete example based on the code from your question:
const formValueKeys = ["name","description","expirationDate",] as const satisfies readonly (keyof FormValues)[];const validate = (values: FormValues) => {const errors: Partial<Record<keyof FormValues, string>> = {};for (const key of formValueKeys) {if (!values[key]) errors[key] = "Required";}return errors;};
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