React setState between components ES6

Question

I have a very simple application where I am trying to update the state of a parent component from a child component as follows:

import React from '../../../../../../../dependencies/node_modules/react';
import ReactDOM from '../../../../../../../dependencies/node_modules/react-dom';

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

    handleClick() {
        this.props.handleStateClick("State Changed");
    }

    render() {
        return ( 
            <div>
                <div className="calendar">
                    {this.props.checkIn}
                    <button onClick={ this.handleClick.bind(this) }>Click Me</button>
                </div>
            </div>
        )
    }
}

class CalendarApp extends React.Component {

    constructor() {
        super();

        this.state = { 
            checkIn: "Check-in",
            checkOut: "Check-out",
            dateSelected: false 
        };
    }

    handleStateClick( newState ) {
        this.setState({
            checkIn: newState
        });
    }

    render() {

        return (
            <div>
                <CalendarMain 
                    checkIn = { this.state.checkIn }
                    handleStateClick = { this.handleStateClick.bind(this) }
                />
            </div>
        );
    }
}

The error I am receiving is this.setState is not a function and I can't work out why. Any help would be much appreciated!

Solution 1

this is not auto-bound in ES6 style syntax.

Either:

1. Bind in constructor like so: this.func = this.func.bind(this)
2. Use arrow function syntax for the function in question like so: func = () => {};

More here: https://facebook.github.io/react/blog/2015/01/27/react-v0.13.0-beta-1.html#autobinding

Solution 2

Use () => lambda to provide lexical scoping and bind correct value of this within the method handleStateClick():

handleStateClick = () => {
  this.setState({
    checkIn: newState
  });
}

Comments

[Sterling Archer]

MDN documentation on arrow functions (lambdas) for more reference

[Felix Kling]

You might want to explain that this feature is experimental and which Babel transforms to include to make this work.

[Felix Kling]

The OP seem to bind it already: handleStateClick = { this.handleStateClick.bind(this) }.

[Aditya Singh]

Assuming that OP is already using ES6 classes and import, one would assume that they have all the prerequisite environment setup

[Felix Kling]

Seems to be a bit of a stretch... are you aware that this is a proposal and not part of ES6?

[Aditya Singh]

I think it is part of ES6 as mentioned here: ecma-international.org/ecma-262/6.0/…. Maybe I am missing something and you can point me to some resource for what you are explaining. If you are referring to the use of transpilers, I think OP has set that up already

[Felix Kling]

The syntax you are suggesting to use seems to be github.com/jeffmo/es-class-fields-and-static-properties . This is currently a stage 1 proposal, so the corresponding plugin or preset has to be added to enable this.