我无法弄清楚如何键入useState
函数,因为它返回一个元组。本质上,我必须提供null
初始值,email
即假设我不能在这里使用空字符串。
然后我有setEmail
更新这个状态值的功能,它将电子邮件作为字符串。
理想情况下,我想输入 my useState
,因此如果可能的话,它希望电子邮件为字符串或 null。目前它只继承它null
import * as React from "react";
const { useState } = React;
function Example() {
const [state, setState] = useState({ email: null, password: null });
function setEmail(email: string) {
setState(prevState => ({ ...prevState, email }))
}
return <p>{state.email}</p>
}
函数返回以下错误,setEmail
因为string
函数参数不是null
指定的有效类型useState()
[ts]
Argument of type '(prevState: { email: null; password: null; }) => { email: string; password: null; }' is not assignable to parameter of type 'SetStateAction<{ email: null; password: null; }>'.
Type '(prevState: { email: null; password: null; }) => { email: string; password: null; }' is not assignable to type '(prevState: { email: null; password: null; }) => { email: null; password: null; }'.
Type '{ email: string; password: null; }' is not assignable to type '{ email: null; password: null; }'.
Types of property 'email' are incompatible.
Type 'string' is not assignable to type 'null'. [2345]
(parameter) prevState: {
email: null;
password: null;
}