javascript - react : Cannot read property 'getWeather' of undefined

Question

我试图弄清楚这种类型错误是从哪里来的，但我似乎无法查明它。也许我错过了 React 的一个重要概念。

我在 React 中有一个天气类:

class Weather extends Component {
  constructor(props) {
    super(props);

    this.state = {
      cityName: "San Francisco",
      temp: null,
    }
  }

  getWeather(city) {
    // does fetch request to openweathermap.org
  }

  handleSubmit(event) {
    event.preventDefault();
    this.getWeather(this.state.cityName);
    // this.state.cityName is updated as the user types
  }
}

问题是每当我单击提交按钮时，我都会收到有关我的 getWeather 函数的错误消息:

TypeError: Cannot read property 'getWeather' of undefined

有什么建议吗？我尝试绑定(bind) getWeather 函数，但没有帮助。

Answer 1

您需要同时绑定(bind)getWeather 和handleSubmit:

  constructor(props) {
    super(props);

    this.state = {
      cityName: "San Francisco",
      temp: null,
    }

    this.getWeather = this.getWeather.bind(this);
    this.handleSubmit = this.handleSubmit.bind(this);
  }