setState outside Component

问题

Im having trouble with the following code:

My compnent:

class Landing extends Component {

  state = {
    loginMethod: '',
    tournamentCode: -1,
  }
}

My Const:

const Code = () => (
  <div className="" style={{marginTop: 20}}>
     <input
      className=""
      style={{lineHeight: 1, height: 30, border:0, paddingLeft: 5}}
      placeholder="Tournament Code"
      onChange={e => this.setState({tournamentCode: e.target.value})} />
    <Link to="/App">
      <button className="" style={{marginLeft: 10, border: 0, outline:        
          'none', background: '#efefef', height: 30, width: 80}}> Enter </button>
    </Link>
  </div>
)

Both of there are in the same Landing.js file.

I know my problem is that i try to do this.setState outside the Landing class. Are there any solutions for this problem? Or is there a better way i should program this?

I've also read some things about redux and contexts in react. Which of these is my best way to go? Or are there more easy solutions?

回答1:

Short answer: No, you cannot setState outside a component.

Long answer: You cannot directly modify the component's state outside it, but you can always create a method that changes the state, then pass it down as props to <Code /> component. Example code (<Link /> component has been removed for simplicity)

import React, { Component } from "react";
import ReactDOM from "react-dom";

class Landing extends Component {
  state = {
    loginMethod: "",
    tournamentCode: -1
  };

  onChange = e => {
    this.setState({
      tournamentCode: e.target.value
    });
  };

  render() {
    //You can use <></> or <React.Fragment></React.Fragment>
    //I printed out the state to show you that it has been updated
    return (
      <>
        <div>{this.state.tournamentCode}</div>
        <Code onChange={this.onChange} />
      </>
    );
  }
}

const Code = ({ onChange }) => (
  <div style={{ marginTop: 20 }}>
    <input
      style={{ lineHeight: 1, height: 30, border: 0, paddingLeft: 5 }}
      placeholder="Tournament Code"
      onChange={onChange}
    />
    <button
      style={{
        marginLeft: 10,
        border: 0,
        outline: "none",
        background: "#efefef",
        height: 30,
        width: 80
      }}
    >
      Enter
    </button>
  </div>
);

const rootElement = document.getElementById("root");
ReactDOM.render(<Landing />, rootElement);

Important: No Redux or context is needed. Learn the basics and try thinking of the most simple solution to a problem, then extend it further. Not in this case, but that's a good learning approach you should apply

Codesandbox for future reference: https://codesandbox.io/s/n1zj5xm24

来源：https://stackoverflow.com/questions/53597482/setstate-outside-component

标签

javascript

reactjs

state