ldo-compact-fork/documentation/solid-react-tutorial.md

Using LDO to build a Solid Application for React

Solid separates the application from the storage, allowing users to put their data wherever they choose. Core to achieving this is application interoparability, the ability to use multiple apps on the same dataset. In order to make applications interoperable, Solid is standardized around RDF (Resource Description Framework), a standard for representing data. While RDF is extremely flexible, it is sometimes cumbersome to work with, that's where LDO (Linked Data Objects) comes in.

In this tutorial, we'll build a web application for Solid using React and LDO. LDO's react library, "@ldobjects/solid-react" is designed to make it easy to manipulate data on a Solid Pod.

We'll be making a simple micro-blogging website that allows you to write notes and upload photos.

// TODO insert image

This tutorial assumes that you are already familiar with React and the overall concepts associated with Solid.

1. Getting Started

First, we'll initialize the project. LDO is designed to work with TypeScript, so we want to initialize a typescript react project.

npx create-react-app my-solid-app --template typescript
cd my-solid-app

2. Setting up a basic app infrastructure

Before we can use LDO and connect to a Solid Pod, let's get the boilerplace React infrastructure out of the way. We'll set up a single page that renders your blog timeline and lets you make new posts, and we'll do this with 5 components:

App.tsx: Base of the application.

import React, { FunctionComponent } from 'react';
import { Header } from './Header';
import { Blog } from './Blog';

export const App: FunctionComponent = () => {
  return (
    <div className="App">
      <Header />
      <Blog />
    </div>
  );
}

Header.tsx: A header component that will help the user log in.

import { FunctionComponent } from "react";

export const Header: FunctionComponent = () => {
  return (
    <header>
      <p>Header</p>
      <hr />
    </header>
  );
};

Blog.tsx: The main place for the blog timeline. We'll use this component to list all posts you've made.

import { FunctionComponent } from "react";
import { MakePost } from "./MakePost";
import { Post } from "./Post";

export const Blog: FunctionComponent = () => {
  return (
    <main>
      <MakePost />
      <hr />
      <Post />
    </main>
  );
};

MakePost.tsx: A form to submit new posts. We've already wired it up with form elements to create a text body and upload an image for the post. We just need to fill out the onSubmit function.

import { FormEvent, FunctionComponent, useCallback, useState } from "react";

export const MakePost: FunctionComponent = () => {
  const [message, setMessage] = useState("");
  const [selectedFile, setSelectedFile] = useState<File | undefined>();

  const onSubmit = useCallback(
    (e: FormEvent<HTMLFormElement>) => {
      e.preventDefault();

      // TODO upload functionality
    },
    [message, selectedFile]
  );

  return (
    <form onSubmit={onSubmit}>
      <input
        type="text"
        placeholder="Make a Post"
        value={message}
        onChange={(e) => setMessage(e.target.value)}
      />
      <input
        type="file"
        accept="image/*"
        onChange={(e) => setSelectedFile(e.target.files?.[0])}
      />
      <input type="submit" value="Post" />
    </form>
  );
};

Post.tsx: A component to render a single post.

import { FunctionComponent } from "react";

export const Post: FunctionComponent = () => {
  return (
    <div>
      <p>Post</p>
    </div>
  );
};

When everything's done, run npm run start and your application should look like this:

Step 3: Installing LDO for Solid and React

With the main infrastructure set up, let's install LDO's Solid/React library.

npm install @ldobjects/solid-react

This library will give us many useful hooks and components for building a Solid application, but it can't be used unless we wrap the application in a provider. Because we're building a React application in the web browser, we'll wrap the application using the BrowserSolidLdoProvider.

App.tsx

// ...
import { BrowserSolidLdoProvider } from '@ldobjects/solid-react';

export const App: FunctionComponent = () => {
  return (
    <div className="App">
      <BrowserSolidLdoProvider>
        <Header />
        <Blog />
      </BrowserSolidLdoProvider>
    </div>
  );
}

4. Implementing Login/Logout in the header

Setting up login for a Solid application is easy when you're using ldo's Solid React library. With the useSolidAuth() hook, you can get information and methods to setup login.

In the component below, we use the session object for information about the current session including session.isLoggedIn, a boolean indicating if the user is currently logged in, and session.webId to get the current user's webId. These will automatically update and rerender the component if anything changes about the current session.

Next we use the login(issuer: string) method to initiate a login. Because a Solid Pod could be anywhere onthe web, we first ask the user to enter their Solid issuer then provide that to the login function.

Finally, the logout() function lets you easily trigger a log out.

Header.tsx

import { useSolidAuth } from "@ldobjects/solid-react";
import { FunctionComponent } from "react";

export const Header: FunctionComponent = () => {
  const { session, login, logout } = useSolidAuth();

  return (
    <header>
      {session.isLoggedIn ? (
        // Is the session is logged in
        <p>
          You are logged in with the webId {session.webId}.{" "}
          <button onClick={logout}>Log Out</button>
        </p>
      ) : (
        // If the session is not logged in
        <p>
          You are not Logged In{" "}
          <button
            onClick={() => {
              // Get the Solid issuer the user should log into
              const issuer = prompt(
                "Enter your Solid Issuer",
                "https://solidweb.me"
              );
              if (!issuer) return;
              login(issuer);
            }}
          >
            Log In
          </button>
        </p>
      )}
      <hr />
    </header>
  );
};

Because useSolidAuth is a hook, you can use it anywhere in the application, even components that don't contain buttons for "login" and "logout." For example, we could use the session object in Blog.tsx to display a message if the user is not logged in.

import { FunctionComponent } from "react";
import { MakePost } from "./MakePost";
import { Post } from "./Post";
import { useSolidAuth } from "@ldobjects/solid-react";

export const Blog: FunctionComponent = () => {
  const { session } = useSolidAuth();
  if (!session.isLoggedIn) return <p>No blog available. Log in first.</p>;

  return (
    <main>
      // ..
    </main>
  );
};

Once you've implemented these changes, the application should look like this when logged out:

And this when logged in:

5. Setting up a shape

In step 6, we're going to use information from a user's Solid WebId profile. But, before we can do that, we want to set up a shape for the Solid Profile.

LDO uses ShEx "Shapes" as schemas to describe how data looks in an application. We can get started by using the init command line tool to get the project ready to use shapes.

npx @ldobjects/cli init