import React, { Component } from ‘react’;

const noop = () => {};

export default class MyComponent extends Component {
  state = { data: null, error: null };

  handleSuccess = data => {
    this.setState({ data });
  };

  handleFailure = error => {
    this.setState({ error });
  };

  componentDidMount() {
    fetch('/api/data')
      .then(data => this.handleSuccess(data))
      .catch(error => this.handleFailure(error));
  }

  componentWillUnmount() {
    this.handleSuccess = noop;
    this.handleFailure = noop;
  }

  render() {
    // ...
  }
}