Guides/Core Curriculum/App School II (Full-Stack)

6. React app setup

Now that we have a basic idea of how Eyre works, we can begin working on our React app front-end.

Create React app

Node.js must be installed, and can be downloaded from their website. With that installed, we'll have the npm package manager available. The first thing we'll do is globally install the create-react-app package with the following command:

npm install -g create-react-app

Once installed, we can use it to create a new journal-ui directory and setup a new React app in it with the following command:

create-react-app journal-ui

We can then open our new directory:

cd journal-ui

Its contents should look something like this:

journal-ui
├── node_modules
├── package.json
├── package-lock.json
├── public
├── README.md
└── src

Install http-api

Inside our React app directory, let's install the @urbit/http-api NPM package:

npm i @urbit/http-api

We also install a handful of other packages for the UI components (bootstrap react-bootstrap react-textarea-autosize date-fns react-bottom-scroll-listener react-day-picker), but that's not important to our purposes here.

Additional tweaks

Our front-end will be served directly from the ship by the %docket app, where a user will open it by clicking on its homescreen tile. Docket serves such front-ends with a base URL path of /apps/[desk]/, so in our case it will be /apps/journal. In order for our app to be built with correct resource paths, we must add the following line to package.json:

"homepage": "/apps/journal/",

Our app also needs to know the name of the ship it's being served from in order to talk with it. The %docket agent serves a small file for this purpose at [host]/session.js. This file is very simple and just contains:

window.ship = "sampel-palnet";

sampel-palnet will of course be replaced by the actual name of the ship. We include this script by adding the following line to the <head> section of public/index.html:

<script src="/session.js"></script>

Basic API setup

With everything now setup, we can begin work on the app itself. In this case we'll just edit the existing App.js file in the /src directory. The first thing is to import the Urbit class from @urbit/http-api:

import Urbit from "@urbit/http-api";

We also need to import a few other things, mostly relating to UI components (but these aren't important for our purposes here):

import React, { Component } from "react";
import "bootstrap/dist/css/bootstrap.min.css";
import "react-day-picker/lib/style.css";
import TextareaAutosize from "react-textarea-autosize";
import Button from "react-bootstrap/Button";
import Card from "react-bootstrap/Card";
import Stack from "react-bootstrap/Stack";
import Tab from "react-bootstrap/Tab";
import Tabs from "react-bootstrap/Tabs";
import ToastContainer from "react-bootstrap/ToastContainer";
import Toast from "react-bootstrap/Toast";
import Spinner from "react-bootstrap/Spinner";
import CloseButton from "react-bootstrap/CloseButton";
import Modal from "react-bootstrap/Modal";
import DayPickerInput from "react-day-picker/DayPickerInput";
import endOfDay from "date-fns/endOfDay";
import startOfDay from "date-fns/startOfDay";
import { BottomScrollListener } from "react-bottom-scroll-listener";

Inside the existing App class:

class App extends Component {

...we'll clear out the existing demo code and start adding ours. The first thing is to define our app's state. We'll look at most of the state entries in the next section. For now, we'll just consider status.

state = {
  // .....
  status: null,
  // .....
};

Next, we'll setup the Urbit API object in componentDidMount. We could do this outside the App class since we're adding it to window, but we'll do it this way so it's all in one place:

componentDidMount() {
  window.urbit = new Urbit("");
  window.urbit.ship = window.ship;
  window.urbit.onOpen = () => this.setState({status: "con"});
  window.urbit.onRetry = () => this.setState({status: "try"});
  window.urbit.onError = (err) => this.setState({status: "err"});
  this.init();
};

The first thing we do is create a new instance of the Urbit class we imported from @urbit/http-api, and save it to window.urbit. The Urbit class constructor takes three arguments: url, desk and code, of which only url is mandatory.

  • url is the URL of the ship we want to talk to. Since our React app will be served by the ship, we can just leave it as an empty "" string and let Urbit use root-relative paths.
  • desk is only necessary if we want to run threads through Eyre, and since we're not going to do that, we can exclude it.
  • code is the web login code for authentication, but since the user will already have logged in, we can also exclude that.

Therefore, we call the class contructor with just the empty url string:

window.urbit = new Urbit("");

Next, we need to set the ship name in our Urbit instance. Eyre requires the ship name be specified in all requests, so if we don't set it, Eyre will reject all the messages we send. We previously included session.js which sets window.ship to the ship name, so we just set window.urbit.ship as that:

window.urbit.ship = window.ship;

Next, we set three callbacks: onOpen, onRetry, and onError. These callbacks are fired when the state of our channel connection changes:

  • onOpen is called when a connection is established.
  • onRetry is called when a channel connection has been interrupted (such as by network issues) and the Urbit object is trying to reconnect. Reconnection will be attempted up to three times: immediately, after 750ms, and after 3000ms.
  • onError is called with an Error message once all retries have failed, or otherwise when a fatal error occurs.

We'll look at how we handle these cases in the next section. For now, we'll just set the status entry in the state to either "con", "try", or "err" as the case may be. Note that it's not mandatory to set these callbacks, but leaving connection problems unhandled is usually a bad idea.

The last thing we do is call:

this.init();

This function will fetch initial entries and subscribe for updates. We'll look at it in the next section.

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5. Eyre

7. React app logic

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