未捕获的TypeError：无法读取null的属性'props'

Question

• I have a react code
• this code renders various panels in the UI.
• when I click a tag, this function is called sportsCornerPanel()
• but I am getting the Uncaught TypeError how to fix it
• providing snippet code below.
• whole code you can see it in the fiddle

code snippet

    sportsCornerPanel() {
        debugger;

        console.log("sportsCornerPanel"
        console.log("this.props.sportsPanelState.size-->" + this.props);

        if (this.props.sportsPanelState.size === 'hidden') {

            if (!this.props.sportsPanelState.visible) {
                this.props.dispatch(sportsOpenPanel());
            } else {
                this.props.dispatch(sportsClosePanel());
            }
        }
    }


    render() {


        let sportsContent, leftNavLink;

        if (this.props.sports-layout !== 'small') {
            console.log("SportsBox---page loads at bigger size");
            console.log("SportsBox---page loads at ipad size");
            sportsContent = <SportsBox className="sports-header"/>;
        } else {
            if (this.props.sportsPanelState.visible) {
                console.log("sportsPanelState--when it becomes small--around ipad width");

                sportsContent = <SportsBox className="sports-nav"/>;
                leftNavLink = <a onClick={this.sportsCornerPanel} href="javascript:;" className="header-navLink active"></a>;
            } else {
                if (this.props.sports.active) {

                    console.log("SportsBox");

                    sportsContent = <SportsBox className="sports-nav"/>;
                } else {

                    console.log("leftNavLink--when it becomes small--around ipad width");

                    leftNavLink = <a onClick={this.sportsCornerPanel} href="javascript:;" className="header-navLink"></a>;
                }
            }
        }


output

Uncaught TypeError: Cannot read property 'props' of null

Answer 1

Since you are not using React.createClass in class methods this doesn't refers to the component instance, so you should bind it manually. There are several ways:

1. Manually bind this in class constructor

constructor(props) {
    super(props);
    this.sportsCornerPanel= this.sportsCornerPanel.bind(this);
}

2. Use ES7 Property initializers with arrow function

sportsCornerPanel = () => {
    debugger;

    console.log("sportsCornerPanel"
    console.log("this.props.sportsPanelState.size-->" + this.props);

    if (this.props.sportsPanelState.size === 'hidden') {

        if (!this.props.sportsPanelState.visible) {
            this.props.dispatch(sportsOpenPanel());
        } else {
            this.props.dispatch(sportsClosePanel());
        }
    }
}

3. Bind this at call-site

In render() method:

    let sportsContent, leftNavLink;

    if (this.props.sports-layout !== 'small') {
        console.log("SportsBox---page loads at bigger size");
        console.log("SportsBox---page loads at ipad size");
        sportsContent = <SportsBox className="sports-header"/>;
    } else {
        if (this.props.sportsPanelState.visible) {
            console.log("sportsPanelState--when it becomes small--around ipad width");

            sportsContent = <SportsBox className="sports-nav"/>;
            leftNavLink = <a onClick={this.sportsCornerPanel.bind(this)} href="javascript:;" className="header-navLink active"></a>;
        } else {
            if (this.props.sports.active) {

                console.log("SportsBox");

                sportsContent = <SportsBox className="sports-nav"/>;
            } else {

                console.log("leftNavLink--when it becomes small--around ipad width");

                leftNavLink = <a onClick={this.sportsCornerPanel.bind(this)} href="javascript:;" className="header-navLink"></a>;
            }
        }
    }

Answer 2

Declare a local variable in constructor for capturing context.

I faced the same issue while using class className extends React.Component instead of createClass() . Create a variable in constructor to fix this.

constructor(props) {
    super(props);
    self = this;
}

Use self.props instead of this.props everywhere!

Answer 3

It looks like you might be missing a getDefaultProps method on your React component. You might consider something generic like this, just to nullify the error and see what else is up:

getDefaultProps () { return {}; }

Answer 4

binding the method in constructor worked absolutely fine.

class Example extends Component {

  constructor(props) {
    super(props);
    this.homeButtonClicked= this.homeButtonClicked.bind(this);
  }
}