profile.js

@connect(
  (state, props) => ({ user: find(propEq('id', Number(props.params.id)), state.users) }),
  { requestUser }
)
export default class UserProfile extends Component {
  static contextTypes = {
    router: React.PropTypes.object
  };

  componentWillMount() {
    // come from another page to /profile/:id
    if (!this.props.user) this.props.requestUser(this.props.params.id)
      .catch(() => this.context.router.push('/notfound'))
  }
  componentWillUpdate(nextProps) {
    // change id param of the route /profile/1 -> /profile/122
    if (!nextProps.user)
      this.props.requestUser(nextProps.params.id)
        .catch(() => this.context.router.push('/notfound'))
  }

  render() {
    return <Profile user={this.props.user}></Profile>
  }
}