175

我正在迁移一个带有 TypeScript 的 React 项目以使用钩子功能(React v16.7.0-alpha),但我无法弄清楚如何设置解构元素的类型。

这是一个例子:

interface IUser {
  name: string;
}
...
const [user, setUser] = useState({name: 'Jon'});

我想强制user变量为 type IUser。我唯一成功的试验是分两个阶段进行:键入,然后初始化:

let user: IUser;
let setUser: any;
[user, setUser] = useState({name: 'Jon'});

但我确信有更好的方法。此外,setUser应该将其初始化为一个以 aIUser作为输入且不返回任何内容的函数。

另外,值得注意的是,在const [user, setUser] = useState({name: 'Jon'});没有任何初始化的情况下使用也可以,但我想利用 TypeScript 来强制对 init 进行类型检查,尤其是在它依赖于某些道具的情况下。

谢谢你的帮助。

4

5 回答 5

371

用这个

const [user, setUser] = useState<IUser>({name: 'Jon'});

DefinitelyTyped中的对应类型

于 2018-12-06T11:35:42.087 回答
30

首先useState需要一个泛型,这将是您的 IUser。如果您想要传递返回的第二个解构元素,则useState需要导入 Dispatch。考虑具有点击处理程序的示例的扩展版本:

import React, { useState, Dispatch } from 'react';

interface IUser {
  name: string;
}

export const yourComponent = (setUser: Dispatch<IUser>) => {

    const [user, setUser] = useState<IUser>({name: 'Jon'});

    const clickHander = (stateSetter: Dispatch<IUser>) => {
        stateSetter({name : 'Jane'});
    }

    return (
         <div>
            <button onClick={() => { clickHander(setUser) }}>Change Name</button>
        </div>
    ) 
}

看到这个答案

于 2019-07-14T01:26:08.637 回答
2

您还可以在之前声明初始状态,然后可以随时调用它:

type User = typeof initUser;
const initUser = {name: 'Jon'}
...
const [user, setUser] = useState<User>(initUser);

关于 I 接口前缀:https ://basarat.gitbooks.io/typescript/content/docs/styleguide/styleguide.html#interface

于 2019-11-26T08:41:30.223 回答
2

https://fettblog.eu/typescript-react/hooks/

// import useState next to FunctionComponent
    import React, { FunctionComponent, useState } from 'react';
    
    // our components props accept a number for the initial value
    const Counter:FunctionComponent<{ initial?: number }> = ({ initial = 0 }) => {
      // since we pass a number here, clicks is going to be a number.
      // setClicks is a function that accepts either a number or a function returning
      // a number
      const [clicks, setClicks] = useState(initial);
      return <>
        <p>Clicks: {clicks}</p>
        <button onClick={() => setClicks(clicks+1)}>+</button>
        <button onClick={() => setClicks(clicks-1)}>-</button>
      </>
    }
于 2020-09-23T06:08:41.770 回答
1
class Form {
    id: NullNumber = null;
    name = '';

    startTime: NullString = null;
    endTime: NullString = null;

    lunchStart: NullString = null;
    lunchEnd: NullString = null;

    [key: string]: string | NullNumber;
}

export const EditDialog: React.FC = () => {
    const [form, setForm] = useState<Form>(new Form());


    const inputChange = (e: ChangeEvent<HTMLInputElement>) => {
        const element = e.target;
        setForm((form: Form) => {
            form[element.name] = element.value;
            return form;
        })
    }
    return (
        <Box pt={3}>
            <TextField
                required
                name="name"
                label="Наименование"
                defaultValue={form.name}
                onChange={inputChange}
                fullWidth
            />
        </Box>
    );
}
于 2021-12-03T15:58:12.857 回答