Using the Simpl Decorator

The simpl decorator allows your app to stay in sync with relevant changes by subscribing to notifications from the modelservice. The UI will receive an action and its store will be updated every time a Scope within a subscribed topic is added, updated or deleted.

In addition to defining your combined Redux reducers and store, you will need a Presentational component that displays progress in loading Simpl data into the Redux store. This component depends on the simpl-react CONNECTION_STATUS property to track progress. The simpl-ui-cookiecutter cookiecutter template provides such a progress component in js/components/Progress.js.

To connect your application to its Redux store and reducers, you must wrap your root Container component in the simpl decorator. The simpl-ui-cookiecutter cookiecutter template does this for you by providing js/modules/Root.js:

import React from 'react';
import PropTypes from 'prop-types';

import {connect} from 'react-redux';
import {Router, Route, browserHistory} from 'react-router';

import {SimplActions} from 'simpl-react/lib/actions';
import {simpl} from 'simpl-react/lib/decorators/simpl';

import Progress from '../components/Progress';


const RootContainer = connect(

const runs = => `${id}`);
const runusers = => `model:model.runuser.${id}`);
const worlds = => `${id}`);
const topics = (LEADER) ? runs : runusers.concat(worlds);
console.log("topics: ", topics);

export default simpl({
  authid: AUTHID,
  password: 'nopassword',
  url: `${MODEL_SERVICE}`,
  progressComponent: Progress,
  root_topic: ROOT_TOPIC,
  topics: () => topics,
  loadAllScenarios: false,
  loadRunDataOnDemand: false

The topics argument passed to the simpl decorator is initialized from Javascript constants defined in the frontend Django app’s templates/frontend/home.html using data returned by the frontend app’s HomeView.get_context_data method in

The loadAllScenarios argument passed to the simpl decorator indicates whether the current user should have access to other users’ scenarios. The default setting of false makes sense for multi-player games. Players in multi-player games typically have access to their own scenarios and their world’s shared scenarios. In multi-player games, leaders typically have access to their own scenarios and to all world scenarios.

The loadRunDataOnDemand argument passed to the simpl decorator controls whether the complete scope tree of all runs the user is in get loaded when a user logs in. By default, all the data of all runs the user is in get loaded. When this argument is set to true, only the user’s runuser and run objects get loaded. Turning this argument on for leaders can speed up their log in process if they are in several runs. To turn off loading the complete run scope trees for leaders, set this argument as follows: loadRunDataOnDemand: LEADER.