passing data from child to parent component - react - via callback function

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passing data from child to parent component via callback function but somehow it's not working. what am I doing wrong here? passing data from child to parent component - react - via callback function

https://codepen.io/silentarrowz/pen/GEMQEP?editors=0010

and here's the code

class App extends React.Component{
    constructor(props){
      super(props);
      this.state={
        input:'this is the input for now'
      }
   //this.handleInput=this.handleInput.bind(this);   
    }

    handleInput(x){
      this.setState({
        input:x
      });
      alert(this.state.input);
    }

  render(){
    return(
      <div>
        <h1>Passing props from Child to Parent Component</h1>
        <Child getInput={this.handleInput} />
        here's the input: {this.state.input}
        </div>
    );
  }
 }

class Child extends React.Component{
  constructor(){
    super();
    this.state={
      text:''
        }
    }
  passingProps(e){
    var newInput=e.target.value;
    //alert(newInput);
   this.setState({
     text:newInput
    });
  this.props.getInput(this.state.text);
  }

  render(){
    return(
      <div>
      <input type="text" placeholder="please input a name..." onChange={this.passingProps} />

        </div>

    )
  }
}

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

There are a couple of issues.

1) You have to bind passingProps

constructor(){
    super();
    this.state={
      text:''
    }
    this.passingProps = this.passingProps.bind(this);
}

2) this.setState is asynchronous, so it's not guaranteed that this.state.text will be set to the value you want by the time you pass it to this.props.getInput. You can either do

this.props.getInput(newInput)

or

this.setState({ text: newInput }, () => {
  this.props.getInput(this.state.text);
})

to resolve that issue.

passing data from child to parent component - react, Passing Data Between React Components — Parent, Children, Siblings From Parent to Child using Props; From Child to Parent using Callbacks Step 2: Also, send the defined callback function as a props to the Child1.js Not surprisingly, to pass data between siblings, you have to use the parent as an intermediary. First pass the data from the child to the parent, as an argument into a callback from the parent. Set

class App extends React.Component{
constructor(props){
  super(props);
  this.state={
    input:'this is the input for now'
  }
  this.handleInput=this.handleInput.bind(this);   
}

handleInput(event){
  let value = event.target.value;
  this.setState({
    input:value
  });
}

render(){
   return(
     <div>
       <h1>{this.state.input}</h1>
       <Child getInput={this.handleInput} />
     </div>
   );
  }
}

 class Child extends React.Component{
   constructor(){
      super(props);
}

render(){
   return(
     <div>
     <input type="text" placeholder="please input a name..." onChange={this.props.getInput} />
    </div>

     )
   }
}

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

Here is the answer for your question. I hope your proplem is solved.

Passing Data Between React Components — Parent, Children , Passing argument from top to bottom is easy via props, but to send data back might seem tricky. Callback to the rescue. Let's reverse engineer it� How to get an updated state of child component in the parent component using the callback method? let's take an example that you have two components Form and input-box having a parent-child relationship.

In your Child Component, you have written following code:

passingProps(e){
  var newInput=e.target.value;
  //alert(newInput);
  this.setState({
     text:newInput
  });
  this.props.getInput(this.state.text);
}

The issue is due to the asynchronous behaviour of setState function. It means you can not call setState on one line and expect its updates on next line. Use the callback function of setState to call the function of parent component just like this:

passingProps(e){
  var newInput=e.target.value;
  //alert(newInput);
  this.setState({ text: newInput }, () => {
     this.props.getInput(this.state.text);
  })
}

Same thing is happening in handleInput function of App component.

Moving Arguments from Child to Parent Component in React, component to another. Data sometimes needs to be able to move from children to parent, parent to… Here is example structure of the React components which comprise my app: App | |__ InputBar Pass that callback as a prop to the child (see above). Call the callback using this.props.[callback] in the� React binds stuff "automagically" for methods you pass as props to child components. Technically callbacks still conform to the React's ideas™ of unidirectional data flow because the context is the parent (not da child) – wle8300 Oct 28 '15 at 1:16

this is not automatically bound in your passingProps function. Try arrow function syntax to bind it.

passingProps = e => {
  var newInput=e.target.value;
  //alert(newInput);
  this.setState({
    text:newInput
  });
  this.props.getInput(this.state.text);
}

Passing Data Between React Components, The child component calls the parent callback function using props. Let's see Passing Data Between React Components — Parent, Children, Siblings. (2020). Teams. Q&A for Work. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information.

Two things that you need to correct it:

  1. if you want to access new state, you don't use this.state.input after this.setState({input: 'xxx'}). Here is reason why not it.
  2. this.passingProps = this.passingProps.bind(this) is defined what this is current scope. when you use this in component's function, this need to be bind.

Changed codepen

Passing Data Between a Parent and Child in React, Pass event handlers and other functions as props to child components: the parent component in the handler, you also need to bind the function to the component Using an arrow function in render creates a new function each time the yes, it is OK, and it is often the easiest way to pass parameters to callback functions. React hooks are introduced in React 16.8. If you are familiar with the class components then there is no difference to change the parent component state from child component. In both cases, you have to pass the callback function to the parent. Let’s take a very simple example to understand it.

Passing Functions to Components – React, The basic idea with React is whenever we have nested components – for In this example, we want to pass our data from to using props. The data we want to pass from our parent to our child is a short list of taco However, if you want to pass data from a child to it's parent, you can use a callback function. Pass event handlers and other functions as props to child components: < button onClick = { this . handleClick } > If you need to have access to the parent component in the handler, you also need to bind the function to the component instance (see below).

Passing Data Between React Components, Published on Apr 4, 2017. Learn how to pass data from child to parent components in react js Duration: 3:49 Posted: Apr 4, 2017 Simply, use this.props.dataFromParent (just a variable used for sending props) to access the data sent from Parent to Child. class Child2 extends React.Component {render() {return (<div> The data from parent is:{this.props.dataFromParent} </div>);}} From Child to Parent Using Callbacks

React JS Tutorial 10: Passing data from child to parent components , passing data from child to parent component - react - via callback function Component{ constructor(props){ super(props); this.state={ input:'this is the input for� React’s one-way data-binding model means that child components cannot send back values to parent components unless explicitly allowed to do so However, if you want to pass data from a child to it’s parent, you can use a callback function. Just pass a function as a prop to the child component.

Comments
  • thanks. that really helped a lot. I didnt know setState is asynchronous
  • @DonovanM hi I'm having a similar issue,but this isn't solving my problem
  • @JohnAnisere what issue are you having? It'll probably be easier to add a new question