reactjs - 从不同文件中的类调用函数 - React
问题描述
我基本上是在尝试从不同文件中的类(时间)调用函数(getValue),但存在一些问题。
这是两个文件的代码:
时间.js
export default class Time extends Component {
constructor(props) {
super(props);
this.state = {
input: '',
input2: '',
checked: false
}
this.getValue = this.getValue.bind(this);
}
hrChange = e => {
this.setState({input: e.target.value}, function () {this.getValue()})
}
minChange = e => {
this.setState({input2: e.target.value}, function () {this.getValue()})
}
amPm = () => {
this.setState({checked: !this.state.checked}, function () {this.getValue()})
}
getValue = () => {
const list = [
this.state.input,
this.state.input2,
this.state.checked
]
return (list)
}
render() {
return(
<text>some stuff</text>
)
}
}
新存储.js
function NewStorage() {
const time = () => {
var obj = new Time();
var list = obj.getValue()
const
hrInput = list[0],
minInput = list[1],
pm = list[2]
return(
console.log(hrInput, minInput, pm, list)
)
return(
time()
)
}
export default NewLocalStorage;
主要问题不是不能调用函数,而是调用函数时,input、input2、checked的值都是原值(''、''、false),而不是更新版本(例如:'11'、'30'、true)。
我不确定如何解决这个问题。
解决方案
您包含react-hooks
标签表明您的预感是钩子适用于解决您的问题。我同意——
const { useState, useEffect } = React
function Time ({ hour, minute, onChange }) {
const [h,setHour] = useState(hour)
const [m,setMinute] = useState(minute)
useEffect(_ => onChange({ hour: h, minute: m }), [h, m])
return <div>
<input value={h} onChange={event => setHour(event.target.value)} />
<input value={m} onChange={event => setMinute(event.target.value)} />
</div>
}
ReactDOM.render(<Time onChange={console.log} />, document.querySelector("main"))
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.14.0/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.14.0/umd/react-dom.production.min.js"></script>
<main></main>
在更复杂的示例中,我们可以使用Time
组件的onChange
回调来更新父组件中的嵌套状态,MyForm
-
const { useState, useEffect, useCallback } = React
function Time ({ hour = 0, minute = 0, onChange }) {
const [h,setHour] = useState(hour)
const [m,setMinute] = useState(minute)
useEffect(_ => onChange({ hour: h, minute: m }), [h, m, onChange])
return <div>
<input value={h} onChange={event => setHour(event.target.value)} />
<input value={m} onChange={event => setMinute(event.target.value)} />
</div>
}
function MyForm () {
const [data, setData] = useState({ time: { hour: 5, minute: 30 }, foo: "bar" })
const onTimeChange = useCallback(t => setData({ ...data, time: t }), [])
return <form>
<Time hour={data.time.hour} minute={data.time.minute} onChange={onTimeChange} />
<pre>{JSON.stringify(data, null, 2)}</pre>
</form>
}
ReactDOM.render(<MyForm />, document.querySelector("main"))
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.14.0/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.14.0/umd/react-dom.production.min.js"></script>
<main></main>