Typescript是对象属性的Type

Question

有可能吗？

const isNotValidated = <T>(req: NextApiRequest, res, schema: any): req.body is T => {}

NextApiRequest不能更改：

declare type NextApiRequest = IncomingMessage & {
    /**
     * Object of `query` values from url
     */
    query: {
        [key: string]: string | string[];
    };
    /**
     * Object of `cookies` from header
     */
    cookies: {
        [key: string]: string;
    };
    body: any;
};

Answer 1

没有用于对象属性的类型保护，但是您可以为整个对象定义保护：

interface NextApiRequestEx<T> extends NextApiRequest {
  body: T;
}

type Bar = { bar: string };

const isNotValidated = <T>(req: NextApiRequest): req is NextApiRequestEx<T> => true;

declare const req: NextApiRequest;

if (isNotValidated<Bar>(req)) {
  req.body.bar // req.body is of type Bar here
}

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