React - How do I access a function in another component?

问题

My structure is as such:

       <ParentComponent />
 <Child 1 />     <Child 2 />

I have a function in <Child 1 />. Since <Child 1 /> controls the grid-layout, and <Child 2 /> is a Navbar with buttons, I want to have a button in <Child 2 /> which will reset some parameters in <Child 1 />.

How do I achieve this? As far as I can see, refs will only be able to go one "step" up the tree, not down.

There isn't any obvious way this function can be invoked from the parent component. Is there any way here? All the solutions I can think of aren't really following the React-mindset, namely the unidirectional data-flow.

回答1:

You can make the parent component as a container for both components. So all the states and functions are handled in the parent components and pass them to the other components as props.

e.g.

    class Parent extends React.Component {

         constructor() {
             super();
             this.state = {
                 controls: controls
             }
         }

         onClick = (dataFromChild2) => {
              //Resetting
              this.setState({controls: dataFromChild2})
         }

         render() {
             return (
                 <div>
                      <Child1 gridControl={this.state.controls}/>
                      <Child2 onClick={this.onClick}/>
                 </div>
             )
         }
    }

You can access the gridControl and onClick from this.props in the children components

UPDATE

Think of it this way, you have the Parent component with the states and function needed to handle the data. The children components take those data and update their states accordingly.

Let's Say the Parent Component is something like this:

class Parent extends React.Component {

  constructor() {
    super();
    this.state = {
      gridControl: {}
    }
  }

  onChild2ButtonClick = (dataFromChild2) => {
    this.setState({
      gridControl: dataFromChild2
    });
  };

  render() {
    return (
      <div>
        <Child1 controls={this.state.gridControl}/>
        <Child2 onClick={this.onChild2ButtonClick}/>
      </div>
    );
  }
}

Child2 Component is something like this:

 class Child2 extends React.Component {
  constructor() {
    super();
  }

  onClick = () => {
    var data = {};
    this.props.onClick(data);
  };

  render() {
    return (
      <div>
        <button onClick={this.onClick}/>
      </div>
    );
  }

If you're using states for Child1, and don't want to change them to props with function in the Parent component to handle them, then you update the state in the componentWillReceivePropsmethod with the new props received from the parent component, so that the props sent will match the states used in Child1 component.

Hope this will clear things up.

回答2:

If your structure looks something as the following:

<ParentComponent>
    <div>
        <Child1 />     
        <Child2 />
    </div>
<ParentComponent />

Both Child1 and Child2 should "communicate" through ParentComponent.
if Child2 will notify ParentComponent about a button click event then it can re-render Child1 with appropiate props accordingly or fire a function that Child1 gets as a prop. this is a basic flow in react.js

As an example consider a House component that has a Button and a Door child components. the Button will toggle opening and closing of the Door.

class House extends Component {

    constructor(props) {
        super(props);

        this.state = {
            isOpened: props.isOpened,
        };

        this.toggleOpenDoor = this.toggleOpenDoor.bind(this);
    }

    toggleOpenDoor() {
        this.setState({
            isOpened: !this.state.isOpened
        });
    }

    render() {
        return (
            <div>
                <Button onClick={this.toggleOpenDoor} />
                <Door isOpened={this.state.isOpened} />
            </div >
        );
    }
}

House.propTypes = {
    isOpened: React.PropTypes.bool
};

House.defaultProps = {
    isOpened: true
};

export default House;

On each change of this.state.isOpened the Door will re-render with the new value as prop

回答3:

METHOD 1: For this you need you need to maintain a store. On clicking button in your <Child2 /> component update the variable in the store. Read the updated variable in the store and if it has change update values in your <Child1 /> component. You can user either flux, redux, mobx etc.. as the store choices, but I would say you can start with redux.

METHOD2:

If you don't want to use store, keep a state in your <Parent /> and on button click in <Child2 /> update your state in parent through a callback function. Pass this state value as props to <Child1 /> and make changes if the prop is present.

来源：https://stackoverflow.com/questions/43657447/react-how-do-i-access-a-function-in-another-component