Visit your Hackathon Blockstack Page for additional resources & prizes.

Complete the Zero to DApp Tutorial

Learn about Blockstack User Authentication

Blockstack Authentication provides single sign on and authentication without third parties or remote servers. Blockstack Authentication is a bearer token-based authentication system. From an app user's perspective, it functions similar to legacy third-party authentication techniques that they're familiar with. For an app developer, the flow is a bit different from the typical client-server flow of centralized sign in services (e.g., OAuth). Rather, with Blockstack, the authentication flow happens entirely client-side.

Learn about Blockstack Storage Methods

Applications built using Blockstack don’t store any user data. Users on Blockstack’s network store their individual application data using a storage system called Gaia that allows a user to store their data wherever they like. The user brings the application specific data to an app each time they authenticate.

This is a hackathon boilerplate for a new Blockstack application created by Major League Hacking in partnership with Blockstack. It is for hackers looking to get started quickly on a new hackathon project using the Blockstack environment.

You are going to build a Decentralized Application (DApp) called Animal Kingdom. Animal Kingdom is a DApp for the web. Users log in and create an animal persona that rules over a specific territory. The combination of persona and territory is a kingdom. Once you create a kingdom, you can add subjects from other kingdoms.

The Animal Kingdom interacts with two Blockstack services, the Blockstack Browser and the Gaia data storage hub. The Blockstack Browser is in itself a DApp. The storage hub is purely a service without user-facing functionality.

Preview the completed version of this application for yourself by using your Blockstack ID. To learn more about this project complete Blockstacks Zero to DApp tutorial.

This project requires the following tools:

• Blockstack ID (Identity) - To test your Animal Kingdom
• NPM - A Node.js package manager used to install dependencies.

To get started, install NPM on your local computer if you don't have them already.

Step 1. Create a Blockstack ID

Open the Blockstack web application in your browser.

Blockstack will will prompt you to create or restore an ID.

Step 2. Install Node Package Manager (NPM).

The Animal Kingdom uses React, Babel, and many other components. You’ll use the npm command to install these packaged components.

Check if you have npm installed by entering the following command in your terminal, and see if you get a response back.

npm -v

If npm is not installed, you can download it here

Step 3. Clone the Animal Kingdom code into a fresh folder

Open your terminal if you haven't already and enter the command below to clone the current repository.

$ git clone https://github.com/MLH/mlh-hackathon-blockstack-starter
$ cd mlh-hackathon-blockstack-starter

Step 4. Install Dependencies

Next, we need to install the project dependencies, which are listed in package.json.

$npm install

In the project directory, you can run

npm start

Open http://localhost:3000 to view it in the browser.

The default port for our app is 3000, but you may need to update this if your setup uses a different port or if you're hosting your app somewhere besides your local machine.

The app will automatically reload if you make changes to the code. You will see the build errors and warnings in the console.

Step 5. Explore the Animal Kingdom

From the initial Animal Kingdom screen, choose an animal persona and a territory, and press done at the bottom of the page.

The Animal Kingdom makes a call to the Gaia hub to store your selection, and returns to your kingdom page. If you have problems, refresh the page and click Your Kingdom in the menu. Spend a little time exploring the application. For example, you could edit your animal or visit the other pages such as Animals or Territories.

Go back to your terminal where your application is running. Press CTRL-Cto stop the application.

Step 6. Customizing your Animal Kingdom

The Animal Kingdom application has two major components, React and Blockstack. React is used to build all the web components and interactions. You could replace React with any framework that you like; Blockstack is web framework agnostic. The blockstack.js library is all a hacker needs to create a DApp. It grants the application the ability to authenticate a Blockstack identity and to read and write to the user’s data stored in a Gaia hub.

Authenticating user identity

The src/app.js file creates a Blockstack UserSession and uses that session's isUserSignedIn() method to determine if the user is signed in or out of the application. Depending on the result of this method. The application redirects to the src/SignedIn page or to the src/Landing.js page.

 import React, { Component } from 'react'
 import './App.css'
 import { UserSession } from 'blockstack'

 import Landing from './Landing'
 import SignedIn from './SignedIn'

 class App extends Component {

   constructor() {
     super()
     this.userSession = new UserSession()
   }

   componentWillMount() {
     const session = this.userSession
     if(!session.isUserSignedIn() && session.isSignInPending()) {
       session.handlePendingSignIn()
       .then((userData) => {
         if(!userData.username) {
           throw new Error('This app requires a username.')
         }
         window.location = `/kingdom/${userData.username}`
       })
     }
   }

   render() {
     return (
       <main role="main">
           {this.userSession.isUserSignedIn() ?
             <SignedIn />
           :
             <Landing />
           }
       </main>
     );
   }
 }

 export default App

Understanding Blockstack Storage

Applications built using Blockstack don’t store any user data. Users on Blockstack’s network store their individual application data using a storage system called Gaia that allows a user to store their data wherever they like. The user brings the application specific data to an app each time they authenticate.

Blockstack JS provides two methods getFile() and putFile() for interacting with Gaia storage. The storage methods support all file types. This means you can store SQL, Markdown, JSON, or even a custom format.

Once a user authenticates, the application can get and put application data in the user’s storage. After a user signs in, the SignedIn.js code checks the user’s Gaia profile by running the loadMe() method.

loadMe() {
    const options = { decrypt: false }
    this.userSession.getFile(ME_FILENAME, options)
    .then((content) => {
      if(content) {
        const me = JSON.parse(content)
        this.setState({me, redirectToMe: false})
      } else {
        const me = null

        this.setState({me, redirectToMe: true})
      }
    })
  }

Most of the imports in this file are locally coded React components. The key Blockstack imports is the UserSession and an appConfig which is defined in the constants.js file.

The loadMe() code uses the Blockstack’s UserSession.getFile() method to get the specified file from the applications data store. If the users’ data store on Gaia does not have the data, which is the case for new users, the Gaia hub responds with HTTP 404 code and the getFile promise resolves to null. If you are using a Chrome Developer Tools with the DApp, you’ll see these errors in a browser’s developer Console.

After a user chooses an animal persona and a territory, the user presses Done and the application stores the user data on Gaia.

saveMe(me) {
  this.setState({me, savingMe: true})
  const options = { encrypt: false }
  this.userSession.putFile(ME_FILENAME, JSON.stringify(me), options)
  .finally(() => {
    this.setState({savingMe: false})
  })
}

The Blockstack putFile() stores the data provided in the user’s DApp data store. You can view the URL for the data store from a user’s profile.

If you tested your Animal Kingdom, you can see this on your profile. To see your profile, go to the Blockstack explorer and search for your ID:

You learned about the Blockstack platform and why it makes Blockchain development a painless process by encapsulating the complexity of the blockstack backend. You have set up a typical development environment for developing a Blockstack web application and ran the Animal Kingdom application locally.

If you would like to customize the Animal Kingdom code follow the Blockstack Zero to DApp tutorial to get started.

Any app built with Blockstack during a hackathon that successfully registers for the App Mining program within two weeks of the event will receive an additional $500 reward. Find your hackathon here

To be eligible, your app must use Blockstack technology and be publicly accessible. If you have an eligible app, you can register it for App Mining here.

• Banter: https://github.com/blockstack-radiks/banter
• Animal Kingdom (This is what is created at the end of the Zero to Dapp tutorial): https://github.com/blockstack/animal-kingdom
• Simple To Do List app: https://github.com/blockstack/blockstack-todos

• Visit the Blockstack forum. This is a valuable resource to learn about the questions that other developers have now or have had in the past.
• Complete the Zero to DApp Tutorial
• Visit your Hackathon Blockstack Page for additional resources & prizes.

We enforce a Code of Conduct for all maintainers and contributors of this Guide. Read more in CONDUCT.md.

The Hackathon Starter Kit is open source software licensed as MIT.

Thank you to our partners Blockstack for providing an in depth tutorial and resources for hackers to use.