call child method from parent

For Hook Parent | Hook Child why do you have to use forwardRef? Why can't you just access the ref inside Child via props.ref and then assign with props.ref.childMethod=childMethod? – Kernel James Mar 8 at 3:40 In this case, the AlertTrait provides one or more traits which it passes down as props to whatever component it was given in its renderComponent prop. https://facebook.github.io/react/tips/expose-component-functions.html for more answers ref here Call methods on React children components

This is our Splunktool team suggestion, we tried and its working fine ✌

//Hope it helps
//This is the child class
public class child {
   public classCall() {
      String str = "I am the child class accessed from parent class!!!";
   }
}
//this the parent class
class parent {
   public static void main(String args[]) {
      child obj = new child(); //objext of child class is created
      System.out.println(obj.classCall()); //'classCall method is called from child class
   }
}

2._

const { forwardRef, useRef, useImperativeHandle } = React;

// We need to wrap component in `forwardRef` in order to gain
// access to the ref object that is assigned using the `ref` prop.
// This ref is passed as the second parameter to the function component.
const Child = forwardRef((props, ref) => {

  // The component instance will be extended
  // with whatever you return from the callback passed
  // as the second argument
  useImperativeHandle(ref, () => ({

    getAlert() {
      alert("getAlert from Child");
    }

  }));

  return <h1>Hi</h1>;
});

const Parent = () => {
  // In order to gain access to the child component instance,
  // you need to assign it to a `ref`, so we call `useRef()` to get one
  const childRef = useRef();

  return (
    <div>
      <Child ref={childRef} />
      <button onClick={() => childRef.current.getAlert()}>Click</button>
    </div>
  );
};

ReactDOM.render(
  <Parent />,
  document.getElementById('root')
);

3._

<script src="https://unpkg.com/react@16/umd/react.development.js" crossorigin></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js" crossorigin></script>

<div id="root"></div>

5._

<script src="https://unpkg.com/react@16/umd/react.development.js" crossorigin></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js" crossorigin></script>
<div id="root"></div>

6._

const { Component } = React;
const { render } = ReactDOM;

class Parent extends Component {
  render() {
    return (
      <div>
        <Child ref={instance => { this.child = instance; }} />
        <button onClick={() => { this.child.getAlert(); }}>Click</button>
      </div>
    );
  }
}

class Child extends Component {
  getAlert() {
    alert('clicked');
  }

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


render(
  <Parent />,
  document.getElementById('app')
);

Suggestion : 2

Use the useImperativeHandle hook in the child to add a function to the Child. We need to forward the ref to the Child so we can use the useImperativeHandle hook to customize the Child's instance value that is exposed to the Parent component when using a ref. To call a child's function from a parent component in React: Call the Child's function from the Parent using the ref, e.g. childRef.current.childFunction().

1._

Copied!import {forwardRef, useImperativeHandle, useRef} from 'react';

const Child = forwardRef((props, ref) => {
  useImperativeHandle(ref, () => ({
    childFunction1() {
      console.log('child function 1 called');
    },
    childFunction2() {
      console.log('child function 2 called');
    },
  }));

  return (
    <div>
      <h2>child content</h2>
    </div>
  );
});

export default function Parent() {
  const childRef = useRef(null);

  const handleClick = () => {
    childRef.current.childFunction1();

    childRef.current.childFunction2();
  };

  return (
    <div>
      <Child ref={childRef} />

      <h2>parent content</h2>

      <button onClick={handleClick}>Call child functions</button>
    </div>
  );
}

2._

Copied!useImperativeHandle(ref, () => ({
   childFunction1() {
      console.log('child function 1 called');
   },
   childFunction2() {
      console.log('child function 2 called');
   },
}));

3._

Copied!import {useEffect, useState} from 'react';

const Child = ({count}) => {
  useEffect(() => {
    const childFunction1 = () => {
      console.log('child function 1 called');
    };

    const childFunction2 = () => {
      console.log('child function 2 called');
    };

    // 👇️ don't run on initial render
    if (count !== 0) {
      childFunction1();

      childFunction2();
    }
  }, [count]);

  return (
    <div>
      <h2>child content</h2>
    </div>
  );
};

export default function Parent() {
  const [count, setCount] = useState(0);

  const handleClick = () => {
    setCount(current => current + 1);
  };

  return (
    <div>
      <Child count={count} />

      <h2>parent content</h2>

      <button onClick={handleClick}>Call child functions</button>
    </div>
  );
}

Suggestion : 3

One way to call a child component's function from its parent is with the help of the useRef hook. Here's the gist of it: We pass a Ref (e.g. childFunc) to a child 🧒 component and assign the desired function to the Ref's current key. This then gives you access to that very function in the parent component. Pay attention to how childFunc is passed down: a custom props is used instead of ref as the latter would otherwise return a DOM element. Take a look at this interactive example:

const Parent = () => {  const childFunc = React.useRef(null)
  return (    <>      <Child childFunc={childFunc} />      <button onClick={() => childFunc.current()}>Click me</button>    </>  )}
const Child = ({ childFunc }) => {  React.useEffect(() => {    childFunc.current = alertUser  }, [])
  function alertUser() {    alert('You clicked!')  }
  return null}
render(<Parent />)

Suggestion : 4

There are two children components and a button to trigger the call. By exporting the component with forwardRef, the Function now has two arguments, props and ref, where the latter needs to be used in useImperativeHandle hook. Well, in this implementation there are some notable things to say: The Class version is pretty straighforward, the method setFromOutside is public, thus, it's visible from the parent by means of the child reference.

1._

import CChild from './CChild'
import FChild from './FChild'

function Mock (props) {
  const fref = useRef()
  const cref = useRef()

  const handleClick = e => {
    fref.current.setFromOutside('HELLO from Parent')
    cref.current.setFromOutside('HELLO from Parent')
  }
  return (
    <div>
      <button onClick={handleClick}>Show Me!</button>
      <FChild ref={fref} />
      <CChild ref={cref} />
    </div>
  )
}

2._

import React from 'react'

class Child extends React.Component {
  constructor (props) {
    super(props)
    this.state = { message: 'Waiting' }
  }

  setFromOutside (msg) {
    this.setState({ message: msg })
  }

  render () {
    return (
      <h1>{this.state.message}</h1>
    )
  }
}
export default Child

3._

import { useState, forwardRef, useImperativeHandle } from 'react'

function Child (props, ref) {
  const [message, setMessage] = useState('Waiting')

  useImperativeHandle(ref, () => ({
    setFromOutside (msg) {
      setMessage(msg)
    }
  }), [])

  return (
    <h1>{message}</h1>
  )
}

export default forwardRef(Child)

Suggestion : 5

We can call methods or functions located inside a child component simply using references which is supported on class components and recently on functional components using hooks. Consider the following child component that contains a method foo which simply alerts a Hello world message. React.createRef() creates the component reference variable which is attached to our child element via the ref attribute. Refs are commonly assigned to an instance property when a component is constructed so they can be referenced throughout the component.

1._

class Child extends React.Component {
  // The child method foo
  foo() {
    alert("Hello world")
  }

  render() {
    return <div>Child content</div>
  }
}

2._

class Parent extends React.Component {

  constructor(props) {
    super(props)

    // Create the child instance using react createRef
    this.child = React.createRef()
  }

  handleClick = () => {

    // Call the child method foo
    this.child.current.foo()
  }

  render() {
    return (
      <>
        <Child ref={this.child} />
        <button onClick={this.handleClick}>
          Call foo
        </button>
      </>
    )
  }

3._

const Child = React.forwardRef((props, ref) => {
  React.useImperativeHandle(ref, () => ({
    foo() {
      alert("Hello world")
    },
  }))

  return <div>Child content</div>
})

Suggestion : 6

When we enclose the child component with forwardRef, it receives a second parameter apart from props, which is the ref passed from the parent component. When you need to call a function declared in the parent component from a child component, it is as easy as passing it as a prop to the child component and calling it from the child component. However, when you want to call the other way around, things can be a bit tricky. In this article, we will see how to the call child component function from the parent component. Let's add a reference to the child component in the parent component using useRef hook.

1._

1const ChildComp = () => {2  function showAlert() {3    alert("Hello from Child Component")4  }5  return <div></div>6}7
8function App() {9  return (10    <div>11      <button>Click Me</button>12      <ChildComp />13    </div>14  )15}16
17export default App

2._

1import { useRef } from "react"2
3const ChildComp = () => {4  function showAlert() {5    alert("Hello from Child Component")6  }7  return <div></div>8}9
10function App() {11  const childCompRef = useRef()12  return (13    <div>14      <button>Click Me</button>15      <ChildComp ref={childCompRef} />16    </div>17  )18}19
20export default App

3._

1import { forwardRef, useRef } from "react"2
3const ChildComp = forwardRef((props, ref) => {4  function showAlert() {5    alert("Hello from Child Component")6  }7  return <div></div>8})9
10function App() {11  const childCompRef = useRef()12  return (13    <div>14      <button>Click Me</button>15      <ChildComp ref={childCompRef} />16    </div>17  )18}19
20export default App

5._

1import { forwardRef, useRef, useImperativeHandle } from "react"2
3const ChildComp = forwardRef((props, ref) => {4  useImperativeHandle(ref, () => ({5    showAlert() {6      alert("Hello from Child Component")7    },8  }))9  return <div></div>10})11
12function App() {13  const childCompRef = useRef()14  return (15    <div>16      <button onClick={() => childCompRef.current.showAlert()}>Click Me</button>17      <ChildComp ref={childCompRef} />18    </div>19  )20}21
22export default App

Suggestion : 7

Give app-child selector in parent. component. html a DOM variable name (prefix with # – hashtag), in this case we call it appChild. Step 1) Create Child component with Aura:Method. Step 2) Create Child Class Controller to Get argument “event. getParam(‘arguments’);” and return the message. Step 3) Create a parent Component and a button to call Aura method. The @ViewChild decorator allows us to inject into a component class references to elements used inside its template, that’s what we should use it for. Using @ViewChild we can easily inject components, directives or plain DOM elements.21-Jan-2022

In this session, we’ll try our hand at solving the Angular Call Child Method From Parent puzzle by using the computer language. The code that follows serves to illustrate this point.

// How to call a child method from a parent component

import {
   ChildComponent
} from '/somepath/childcomponent.ts';

export class ParentComponent implements onInit {

   @ViewChild(ChildComponent) ChildComponent;

   this.ChildComponent.childMethod();

Suggestion : 8

Good day, folks. In this post, we’ll examine how to find a solution to the programming challenge titled Angular Call Child Method From Parent. We were able to demonstrate how to correct the Angular Call Child Method From Parent bug by looking at a variety of examples taken from the real world. Angular Call Child Method From Parent With Code Examples Background Image With Styled Components With Code Examples

// How to call a child method from a parent component

import {
   ChildComponent
} from '/somepath/childcomponent.ts';

export class ParentComponent implements onInit {

   @ViewChild(ChildComponent) ChildComponent;

   this.ChildComponent.childMethod();