删除Dealloc中的Observer

import React, { Component } from 'react';

class MyComponent extends Component {
  constructor(props) {
    super(props);
    this.state = {
      data: null,
    };
  }

  componentDidMount() {
    // 订阅数据源
    dataSource.addObserver(this);
  }

  componentWillUnmount() {
    // 取消订阅数据源
    dataSource.removeObserver(this);
  }

  update(data) {
    this.setState({ data });
  }

  render() {
    const { data } = this.state;
    return (
      <div>
        {data ? data.toString() : 'Loading...'}
      </div>
    );
  }
}

export default MyComponent;