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。

从父函数触发子函数的另一种方法是在子组件中使用componentDidUpdate函数。我将一个道具triggerChildFunc从父对象传递给子对象，初始值为null。当单击按钮时，该值更改为一个函数，Child注意到componentDidUpdate中的更改并调用自己的内部函数。

因为道具triggerChildFunc变成了一个函数，我们也得到了一个回调到父类的函数。如果Parent不需要知道函数何时被调用，则triggerChildFunc值可以从null改为true。

const { Component } = React; const { render } = ReactDOM; class Parent extends Component { state = { triggerFunc: null } render() { return ( <div> <Child triggerChildFunc={this.state.triggerFunc} /> <button onClick={() => { this.setState({ triggerFunc: () => alert('Callback in parent')}) }}>Click </button> </div> ); } } class Child extends Component { componentDidUpdate(prevProps) { if (this.props.triggerChildFunc !== prevProps.triggerChildFunc) { this.onParentTrigger(); } } onParentTrigger() { alert('parent triggered me'); // Let's call the passed variable from parent if it's a function if (this.props.triggerChildFunc && {}.toString.call(this.props.triggerChildFunc) === '[object Function]') { this.props.triggerChildFunc(); } } render() { return ( <h1>Hello</h1> ); } } render( <Parent />, document.getElementById('app') ); <script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script> <div id='app'></div>

CodePen: https://codepen.io/calsal/pen/NWPxbJv?editors=1010

我们可以用另一种方式使用refs，如-

我们将创建一个父元素，它将呈现一个<Child/>组件。如您所见，对于将要呈现的组件，您需要添加ref属性并为其提供名称。 然后，位于父类中的triggerChildAlert函数将访问this context的refs属性(当triggerChildAlert函数被触发时，它将访问子引用，并且它将具有子元素的所有函数)。

class Parent extends React.Component {
    triggerChildAlert(){
        this.refs.child.callChildMethod();
        // to get child parent returned  value-
        // this.value = this.refs.child.callChildMethod();
        // alert('Returned value- '+this.value);
    }

    render() {
        return (
            <div>
                {/* Note that you need to give a value to the ref parameter, in this case child*/}
                <Child ref="child" />
                <button onClick={this.triggerChildAlert}>Click</button>
            </div>
        );
    }
}  

现在，子组件，就像之前理论上设计的那样，看起来像:

class Child extends React.Component {
    callChildMethod() {
        alert('Hello World');
        // to return some value
        // return this.state.someValue;
    }

    render() {
        return (
            <h1>Hello</h1>
        );
    }
}

这里是源代码- 希望对你有所帮助!

使用useEffect的替代方法:

家长:

const [refresh, doRefresh] = useState(0);
<Button onClick={() => doRefresh(prev => prev + 1)} />
<Children refresh={refresh} />

孩子们:

useEffect(() => {
    performRefresh(); //children function of interest
  }, [props.refresh]);

I wasn't satisfied with any of the solutions presented here. There is actually a very simple solution that can be done using pure Javascript without relying upon some React functionality other than the basic props object - and it gives you the benefit of communicating in either direction (parent -> child, child -> parent). You need to pass an object from the parent component to the child component. This object is what I refer to as a "bi-directional reference" or biRef for short. Basically, the object contains a reference to methods in the parent that the parent wants to expose. And the child component attaches methods to the object that the parent can call. Something like this:

// Parent component.
function MyParentComponent(props) {

   function someParentFunction() {
      // The child component can call this function.
   }

   function onButtonClick() {
       // Call the function inside the child component.
       biRef.someChildFunction();
   }

   // Add all the functions here that the child can call.
   var biRef = {
      someParentFunction: someParentFunction
   }

   return <div>
       <MyChildComponent biRef={biRef} />
       <Button onClick={onButtonClick} />
   </div>;
}


// Child component
function MyChildComponent(props) {

   function someChildFunction() {
      // The parent component can call this function.
   }


   function onButtonClick() {
      // Call the parent function.
      props.biRef.someParentFunction();
   }

   // Add all the child functions to props.biRef that you want the parent
   // to be able to call.
   props.biRef.someChildFunction = someChildFunction;

   return <div>
       <Button onClick={onButtonClick} />
   </div>;
}

这种解决方案的另一个优点是，您可以在父节点和子节点中添加更多的函数，同时只使用一个属性将它们从父节点传递给子节点。

对上述代码的改进是不直接向biRef对象添加父函数和子函数，而是向子成员添加。父函数应该添加到名为“Parent”的成员中，而子函数应该添加到名为“child”的成员中。

// Parent component.
function MyParentComponent(props) {

   function someParentFunction() {
      // The child component can call this function.
   }

   function onButtonClick() {
       // Call the function inside the child component.
       biRef.child.someChildFunction();
   }

   // Add all the functions here that the child can call.
   var biRef = {
      parent: {
          someParentFunction: someParentFunction
      }
   }

   return <div>
       <MyChildComponent biRef={biRef} />
       <Button onClick={onButtonClick} />
   </div>;
}


// Child component
function MyChildComponent(props) {

   function someChildFunction() {
      // The parent component can call this function.
   }


   function onButtonClick() {
      // Call the parent function.
      props.biRef.parent.someParentFunction();
   }

   // Add all the child functions to props.biRef that you want the parent
   // to be able to call.
   props.biRef {
       child: {
            someChildFunction: someChildFunction
       }
   }

   return <div>
       <Button onClick={onButtonClick} />
   </div>;
}

通过将父函数和子函数放在biRef对象的独立成员中，您将在两者之间有一个清晰的分离，并且很容易看到哪个属于父函数或子函数。如果父组件和子组件中都出现了相同的函数，它还有助于防止子组件意外地覆盖父函数。

One last thing is that if you note, the parent component creates the biRef object with var whereas the child component accesses it through the props object. It might be tempting to not define the biRef object in the parent and access it from its parent through its own props parameter (which might be the case in a hierarchy of UI elements). This is risky because the child may think a function it is calling on the parent belongs to the parent when it might actually belong to a grandparent. There's nothing wrong with this as long as you are aware of it. Unless you have a reason for supporting some hierarchy beyond a parent/child relationship, it's best to create the biRef in your parent component.

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>
  );
 }
}