index.js

import React, { Component } from 'react';

// Conectando el componente a reducer
import { connect } from 'react-redux';

import * as usuariosActions from '../../actions/usuariosActions';
import Spinner from '../general/Spinner';
import Fatal from '../general/Fatal';
import Tabla from './Tabla';

class Users extends Component {

  componentDidMount() {
    if (!this.props.usuarios.length) {
      this.props.traerTodos();
    }
  }

  ponerContenido = () => {

    if (this.props.cargando) {
      return <Spinner />;
    }

    if (this.props.error) {
      return <Fatal mensaje={this.props.error} />;
    }

    return <Tabla />;
  }

  render() {
    return (
      <div>
        <h1>Usuarios</h1>
        {this.ponerContenido()}
      </div>
    );
  }
}

const mapStateToProps = (reducer) => {
  return reducer.usuariosReducer;
}

export default connect(mapStateToProps, usuariosActions/*Actions*/)(Users);