React - uncaught TypeError：无法读取undefined的属性'setState' [英] React - uncaught TypeError: Cannot read property 'setState' of undefined

问题描述

我收到以下错误

未捕获的TypeError：无法读取未定义的属性'setState'

Uncaught TypeError: Cannot read property 'setState' of undefined

甚至在构造函数中绑定delta之后。

even after binding delta in the constructor.

class Counter extends React.Component {
    constructor(props) {
        super(props);

        this.state = {
            count : 1
        };

        this.delta.bind(this);
    }

    delta() {
        this.setState({
            count : this.state.count++
        });
    }

    render() {
        return (
            <div>
                <h1>{this.state.count}</h1>
                <button onClick={this.delta}>+</button>
            </div>
        );
    }
}

推荐答案

这是由于 this.delta 没有被绑定到这个。

This is due to this.delta not being bound to this.

为了在构造函数中绑定set this.delta = this.delta.bind（this）：

In order to bind set this.delta = this.delta.bind(this) in the constructor:

constructor(props) {
    super(props);

    this.state = {
        count : 1
    };

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

目前，您正在调用bind。但是bind返回一个绑定函数。您需要将函数设置为其绑定值。

Currently, you are calling bind. But bind returns a bound function. You need to set the function to its bound value.

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