[英]How to convert object of any type values, to object of string values (Typescript)?
I have an object.我有一个 object。
let obj1: A;
/*
type A = {
property1: any;
property2: any;
}
*/
I know that the values in the object are all strings, but I don't want to forcefully typecast.我知道 object 中的值都是字符串,但我不想强制类型转换。
// I don't want to do this
const obj2 = obj1 as Record<keyof typeof obj1, string>
Instead, I want to infer it in the right way, using typescript predicates .相反,我想以正确的方式推断它,使用typescript 谓词。 This is my attempt to do it.
这是我的尝试。
function getIsCorrectType<T extends Record<string, any>>(
obj: T
): obj is Record<keyof T, string>{
return true; // assume that I manually checked each value to be a string
}
However I now get an error但是我现在得到一个错误
A type predicate's type must be assignable to its parameter's type.
Type 'Record<keyof T, string>' is not assignable to type 'T'.
'Record<keyof T, string>' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint 'Record<string, any>'.
Type 'string' is not assignable to type 'T[P]'.
To me this sounds crazy.对我来说这听起来很疯狂。 I should be able to assign
string
to T[P] = any
, right?我应该能够将
string
分配给T[P] = any
,对吧? What am I doing wrong?我究竟做错了什么? Is there any alternative solution to this?
有没有其他解决方案?
In order to make it work, you need to infer just a set of keys instead of whole object:为了使其工作,您只需要推断一组键而不是整个 object:
const isString = (value: unknown): value is string => typeof value === 'string'
const getIsCorrectType = <K extends string>(
obj: Record<K, unknown>
): obj is Record<K, string> =>
Object.values(obj).every(isString)
const x = getIsCorrectType({ 1: 'sdf' })
K
- is used for keys inference K
- 用于键推断
Also I have added isString
custom typeguard我还添加了
isString
自定义类型保护
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