将道具从组件传递到组件| 反应

Question

I want to pass the props or function of an main component to child component to work. totally i need to pass the props over three component to reach its child component. Below is my code, which not working properly. I think, my code will say, what i want to achieve.

If I want to achieve the same thing in single component, it works well. But, when i try to break into different components, i couldn't make it. I making mistake, while passing props.

Thanks In Advance.

/**Home Component**/

class Home extends Component {

    constructor(props) {
        super(props);
        this.state = {
            value: null,
            componentToRender: null //tells switch which component to render
        };
        this.renderComponent = this.renderComponent.bind(this)
    };

    handleEvent = (button) => {
        this.setState({value: button});
    };
    handleClick = () => {
        this.setState({componentToRender: this.state.value})//take the
        // currently selected component and make it the component to render
    };
        //extract the switch statement to a method of its own
    renderComponent() {
        switch (this.state.componentToRender) {
            case 0:
                return 'cool';
            case 1:
                return 'not cool';
            case 2:
                return 'medium cool';
            default:
                return <ComponentOne toRender={this.state.componentToRender} />;
        }
    }

    render() {
        return (
            <div>

                {this.renderComponent()}
            </div>
        );
       }
      }


      export default Home;

/**Component one***/
import ComponentTwo from './ComponentTwo.js'
class ComponentOne extends Component {
render(){
return (
<ComponentTwo toRender={this.state.componentToRender}/>
 );
}
}
export default ComponentOne;

/**Component two***/

import ComponentThree from './ComponentThree.js'
class ComponentTwo extends Component {
render(){
return (
<ComponentThree toRender={this.state.componentToRender}/>
);
}
}
export default ComponentTwo;


/**Component three***/
class ComponentThree extends Component {

 constructor(props){
    super(props);
    this.state = {
        value: null,
    };
    };

    handleEvent = (button) => {
      this.setState({value: button});
  };

    handleClick = () => {
      this.setState({componentToRender: this.state.value});
  };
render(){
return (
 <div >
                    <button onClick={() => this.handleEvent(0)}>Component
                        One</button>
                    <button onClick={() => this.handleEvent(1)}>Component
                        Two</button>
                    <button onClick={() => this.handleEvent(2)}>Component
                        three</button>
                    <button onClick={() => this.handleEvent(3)}>Component
                        Four</button>

                    <button variant="contained" onClick={this.handleClick}>
                        Register Now
                    </button>
                </div>
);
}
}
export default Componentthree;

Answer 1

ComponentThree is setting its own state, not the state of Home . Since nothing changes the state of Home , it will always render the same thing.

If you want to update the state of a parent component from within a child component, you must pass down the update callback as a prop. In this case, you'd need to pass the handleClick down from Home to ComponentThree , and then use that as the click handler for the buttons.

Also, you're trying to read componentToRender from this.state in your child components - you need to use this.props , as you're passing the values down as props.

It's also worth noting that a React Context can be useful when trying to make state available to deeply nested components - that said, they're not something you should overuse, and I'd recommend getting the hang of passing things around as props before trying to dive in to using Contexts.