我有两个组成部分:
父组件
子组件
我试图从Parent调用Child的方法,我尝试了这种方式,但不能得到一个结果:
class Parent extends Component {
render() {
return (
<Child>
<button onClick={Child.getAlert()}>Click</button>
</Child>
);
}
}
class Child extends Component {
getAlert() {
alert('clicked');
}
render() {
return (
<h1 ref="hello">Hello</h1>
);
}
}
是否有一种方法从父调用子方法?
注意:子组件和父组件在两个不同的文件中。
你可以很容易地使用你的子组件作为react自定义钩子来应用这个逻辑。
如何实施?
子函数返回一个函数。
子函数返回JSON:{函数、HTML或其他值}作为示例。
在这个例子中,应用这个逻辑没有意义,但很容易看出:
const {useState} = React;
//Parent
const Parent = () => {
//custome hook
const child = useChild();
return (
<div>
{child.display}
<button onClick={child.alert}>
Parent call child
</button>
{child.btn}
</div>
);
};
//Child
const useChild = () => {
const [clickCount, setClick] = React.useState(0);
{/* child button*/}
const btn = (
<button
onClick={() => {
setClick(clickCount + 1);
}}
>
Click me
</button>
);
return {
btn: btn,
//function called from parent
alert: () => {
alert("You clicked " + clickCount + " times");
},
display: <h1>{clickCount}</h1>
};
};
const rootElement = document.getElementById("root");
ReactDOM.render(<Parent />, rootElement);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.8.4/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.8.4/umd/react-dom.production.min.js"></script>
<div id="root"></div>
这里是我的演示:https://stackblitz.com/edit/react-dgz1ee?file=styles.css
I am using useEffect to call the children component's methods. I have tried with Proxy and Setter_Getter but sor far useEffect seems to be the more convenient way to call a child method from parent. To use Proxy and Setter_Getter it seems there is some subtlety to overcome first, because the element firstly rendered is an objectLike's element through the ref.current return => <div/>'s specificity.
Concerning useEffect, you can also leverage on this approach to set the parent's state depending on what you want to do with the children.
在我提供的演示链接中,你会发现我完整的ReactJS代码和我的草稿,所以你可以欣赏我的解决方案的工作流程。
在这里,我只提供了相关代码的ReactJS片段。:
import React, {
Component,
createRef,
forwardRef,
useState,
useEffect
} from "react";
{...}
// Child component
// I am defining here a forwardRef's element to get the Child's methods from the parent
// through the ref's element.
let Child = forwardRef((props, ref) => {
// I am fetching the parent's method here
// that allows me to connect the parent and the child's components
let { validateChildren } = props;
// I am initializing the state of the children
// good if we can even leverage on the functional children's state
let initialState = {
one: "hello world",
two: () => {
console.log("I am accessing child method from parent :].");
return "child method achieve";
}
};
// useState initialization
const [componentState, setComponentState] = useState(initialState);
// useEffect will allow me to communicate with the parent
// through a lifecycle data flow
useEffect(() => {
ref.current = { componentState };
validateChildren(ref.current.componentState.two);
});
{...}
});
{...}
// Parent component
class App extends Component {
// initialize the ref inside the constructor element
constructor(props) {
super(props);
this.childRef = createRef();
}
// I am implementing a parent's method
// in child useEffect's method
validateChildren = childrenMethod => {
// access children method from parent
childrenMethod();
// or signaling children is ready
console.log("children active");
};
{...}
render(){
return (
{
// I am referencing the children
// also I am implementing the parent logic connector's function
// in the child, here => this.validateChildren's function
}
<Child ref={this.childRef} validateChildren={this.validateChildren} />
</div>
)
}
你可以在这里使用另一个模式:
class Parent extends Component {
render() {
return (
<div>
<Child setClick={click => this.clickChild = click}/>
<button onClick={() => this.clickChild()}>Click</button>
</div>
);
}
}
class Child extends Component {
constructor(props) {
super(props);
this.getAlert = this.getAlert.bind(this);
}
componentDidMount() {
this.props.setClick(this.getAlert);
}
getAlert() {
alert('clicked');
}
render() {
return (
<h1 ref="hello">Hello</h1>
);
}
}
它所做的是在挂载子节点时设置父节点的clickChild方法。这样,当你点击parent中的按钮时,它会调用clickChild,它会调用child的getAlert。
如果你的子文件是用connect()包装的,那么你就不需要getWrappedInstance()了。
注意你不能使用onClick={this。在父元素中使用clickChild},因为当父元素被渲染时,子元素不会被挂载,所以这个。clickChild还没有被分配。使用onClick={() => this. clickchild()}是好的,因为当你点击按钮this. clickchild()}。clickChild应该已经被分配了。
您可以使用ref从父组件调用子组件的函数
功能组件解决方案
在函数组件中,你必须使用useImperativeHandle来获取引用到如下所示的子组件中
import React, { forwardRef, useRef, useImperativeHandle } from 'react';
export default function ParentFunction() {
const childRef = useRef();
return (
<div className="container">
<div>
Parent Component
</div>
<button
onClick={() => { childRef.current.showAlert() }}
>
Call Function
</button>
<Child ref={childRef}/>
</div>
)
}
const Child = forwardRef((props, ref) => {
useImperativeHandle(
ref,
() => ({
showAlert() {
alert("Child Function Called")
}
}),
)
return (
<div>Child Component</div>
)
})
类组件解决方案
Child.js
import s from './Child.css';
class Child extends Component {
getAlert() {
alert('clicked');
}
render() {
return (
<h1>Hello</h1>
);
}
}
export default Child;
Parent.js
class Parent extends Component {
render() {
onClick() {
this.refs.child.getAlert();
}
return (
<div>
<Child ref="child" />
<button onClick={this.onClick}>Click</button>
</div>
);
}
}