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Blockstack Storage Tutorial

{:.no_toc}

In this tutorial, you build a micro-blogging application using multi-player Gaia storage. Gaia is Blockstack's decentralized high-performance storage system. The tutorial contains the following topics:

TOC {:toc}

This tutorial does not teach you about authentication. That is covered in depth in the hello-blockstack tutorial.

{% include note.html content="This tutorial was written on macOS High Sierra 10.13.4. If you use a Windows or Linux system, you can still follow along. However, you will need to "translate" appropriately for your operating system. Additionally, this tutorial assumes you are accessing the Blockstack Browser web application via Chrome. The application you build will also work with a local installation and/or with browsers other than Chrome. " %}

About this tutorial and the prerequisites you need

The storage application you build with this tutorial is a React.js application that is completely decentralized and server-less. While not strictly required to follow along, basic familiarity with React.js is helpful.

When complete, the app is capable of the following:

authenticating users using Blockstack
posting new statuses
displaying statuses in the user profile
looking up the profiles and statuses of other users

The basic identity and storage services are provided by blockstack.js. To test the application, you need to have already registered a Blockstack ID.

The tutorial relies on the npm dependency manager. Before you begin, verify you have installed npm using the which command.

$ which npm
/usr/local/bin/npm

If you don't find npm in your system, install it. Finally, if you get stuck at any point while working on the tutorial, the completed source code is available for you to check your work against. You can also try out the live build of the app.

Use npm to install Yeoman and the Blockstack App Generator

You use npm to install Yeoman. Yeoman is a generic scaffolding system that helps users rapidly start new projects and streamline the maintenance of existing projects.

Install Yeoman.
```
npm install -g yo
```
Install the Blockstack application generator.
```
npm install -g generator-blockstack
```

Generate and launch the public application

In this section, you build an initial React.js application called Publik.

Create a the publik directory.
```
mkdir publik
```
Change into your new directory.
```
cd publik
```

Use Yeoman and the Blockstack application generator to create your initial publik application.

yo blockstack:react

You should see several interactive prompts.

$ yo blockstack:react
? ==========================================================================
We're constantly looking for ways to make yo better!
May we anonymously report usage statistics to improve the tool over time?
More info: https://github.com/yeoman/insight & http://yeoman.io
========================================================================== No

     _-----_     ╭──────────────────────────╮
    |       |    │      Welcome to the      │
    |--(o)--|    │      Blockstack app      │
   `---------´   │        generator!        │
    ( _´U`_ )    ╰──────────────────────────╯
    /___A___\   /
     |  ~  |
   __'.___.'__
 ´   `  |° ´ Y `

? Are you ready to build a Blockstack app in React? (Y/n)

Respond to the prompts to populate the initial app.

After the process completes successfully, you see a prompt similar to the following:

[fsevents] Success:
"/Users/theuser/repos/publik/node_modules/fsevents/lib/binding/Release/node-v59-darwin-x64/fse.node"
is installed via remote npm notice created a lockfile as package-lock.json.
You should commit this file. added 1060 packages in 26.901s

Run the initial application.
```
npm start
```
The system may prompt you to accept incoming connections.
If it does, choose Allow.
Your browswer –– Chrome by default –– will open to http://127.0.0.1:3000/.

You should see a simple React app.
Choose Sign In with Blockstack.

The application tells you it will Read your basic info.

Leave your new application running and move onto the next section.

Add the `publish_data` scope to sign in requests

Any Blockstack app can use Gaia storage, but those apps that need to share data publicly must add themselves to the user's profile.json file. The Blockstack Browser does this automatically when the publish_data scope is requested during authentication. For this application, the user files stored on Gaia are made visible to others via the apps property in the user's profile.json file.

Modify your authentication request to include the publish_data scope.

Open src/components/App.js file.
Locate the AppConfig declaration near the beginning of the file.
```
const appConfig = new AppConfig()
```
Change it to this:
```
const appConfig = new AppConfig(['store_write', 'publish_data'])
```
By default, authentication requests include the store_write scope which enables storage. This is what allows you to store information to Gaia. Adding the publish_data scope allows your app to share data between users.
Save your changes.
Go back to your app at http://127.0.0.1:3000/.
Log out and sign in again.

The authentication request now prompts the user for permission to Publish data stored for the app.

Understand Gaia storage methods

Once you authenticate a user with store_write and publish_data, you can begin to manage data for your users. Blockstack JS provides two methods within the UserSession class, UserSession.getFile and UserSession.putFile for interacting with Gaia storage. The storage methods support all file types. This means you can store markdown, JSON, or even a custom format.

You can create a meaningful and complex data layer using these two methods. Before creating an application, consider fundamental data architecture and make some decisions about how you’re modeling data. For example, consider building a simple grocery list app. A user should be able to create, read, update, and delete grocery lists.

A single file collection stores items as an array nested inside each grocery list:

// grocerylists.json
{
  "3255": {
    "items": [
      "1 Head of Lettuce",
      "Haralson apples"
    ]
  },
  // ...more lists with items
}

This is conceptually the simplest way to manage grocery lists. When you read a /grocerylists.json file with getFile(), you get back one or more grocery lists and their items. When you write a single list, the putFile() method overwrites the entire list. So, a write operation for a new or updated grocery list must submit all existings lists as well.

Further, because this runs on the client where anything can go wrong. If the client-side code encounters a parsing error with a user-input value and you could overwrite the entire file with:

line 6: Parsing Error: Unexpected token.

Further, a single file makes pagination impossible and if your app stores a single file for all list you have less control over file permissions. To avoid these issues, you can create an index file that stores an array of IDs. These IDs point to a name of another file in a grocerylists folder.

This design allows you to get only the files you need and avoid accidentally overwriting all lists. Further, you’re only updating the index file when you add or remove a grocery list; updating a list has no impact.

Add support for user status submission and lookup

In this step, you add three blockstack.js methods that support posting of "statuses". These are the UserSession.putFile, UserSession.getFile, and lookupProfile methods.

Open the src/components/Profile.js file.

Replace the initial state in the constructor() method so that it holds the key properties required by the app.

This code constructs a Blockstack Person object to hold the profile. Your constructor should look like this:

constructor(props) {
  super(props);

  this.state = {
    person: {
      name() {
        return 'Anonymous';
      },
      avatarUrl() {
        return avatarFallbackImage;
      },
    },
    username: "",
    newStatus: "",
    statuses: [],
    statusIndex: 0,
    isLoading: false
  };
}

Locate the render() method.

Modify the render() method to add a text input and submit button to the by replacing it with the code below:

The following code renders the person.name and person.avatarURL properties from the profile on the display:

render() {
  const { handleSignOut, userSession } = this.props;
  const { person } = this.state;
  const { username } = this.state;

  return (
    !userSession.isSignInPending() && person ?
    <div className="container">
      <div className="row">
        <div className="col-md-offset-3 col-md-6">
          <div className="col-md-12">
            <div className="avatar-section">
              <img
                src={ person.avatarUrl() ? person.avatarUrl() : avatarFallbackImage }
                className="img-rounded avatar"
                id="avatar-image"
              />
              <div className="username">
                <h1>
                  <span id="heading-name">{ person.name() ? person.name()
                    : 'Nameless Person' }</span>
                  </h1>
                <span>{username}</span>
                <span>
                  &nbsp;|&nbsp;
                  <a onClick={ handleSignOut.bind(this) }>(Logout)</a>
                </span>
              </div>
            </div>
          </div>

          <div className="new-status">
            <div className="col-md-12">
              <textarea className="input-status"
                value={this.state.newStatus}
                onChange={e => this.handleNewStatusChange(e)}
                placeholder="Enter a status"
              />
            </div>
            <div className="col-md-12">
              <button
                className="btn btn-primary btn-lg"
                onClick={e => this.handleNewStatusSubmit(e)}
              >
                Submit
              </button>
            </div>
          </div>

        </div>
      </div>
    </div> : null
  );
}

This code allows the application to post statuses. It also displays the user's Blockstack ID. To display this, your app must extract the ID from the user profile data.

Notice that the userSession property passed into our profile renderer contains the isSignInPending() method which checks if a sign in operation is pending.

Locate the componentWillMount() method.

Add the username property below the person property.

You'll use the Blockstack loadUserData() method in our user session to access the username.

componentWillMount() {
  const { userSession } = this.props
  this.setState({
    person: new Person(userSession.loadUserData().profile),
    username: userSession.loadUserData().username
  });
}

Add two methods in the Profile class to handle the status input events:

handleNewStatusChange(event) {
  this.setState({newStatus: event.target.value})
}

handleNewStatusSubmit(event) {
  this.saveNewStatus(this.state.newStatus)
  this.setState({
    newStatus: ""
  })
}

Add a saveNewStatus() method to save the new statuses.

saveNewStatus(statusText) {
  const { userSession } = this.props
  let statuses = this.state.statuses

  let status = {
    id: this.state.statusIndex++,
    text: statusText.trim(),
    created_at: Date.now()
  }

  statuses.unshift(status)
  const options = { encrypt: false }
  userSession.putFile('statuses.json', JSON.stringify(statuses), options)
    .then(() => {
      this.setState({
        statuses: statuses
      })
    })
}

Save the Profile.js file.

After the application compiles successfully, your application should appears as follows:
Enter your status in the text box and press the Submit button.

At this point, the status you've just submitted isn't being displayed. In the next section you add code to display the statuses back to the user as a blog entry.

Fetch and display statuses

Update Profile.js again.

Go back to the render() method.
Locate the <div className="new-status"> containing the text input and Submit button.

Right before the matching closing </div> element in this section, add this block.

<div className="col-md-12 statuses">
  {this.state.isLoading && <span>Loading...</span>}
  {this.state.statuses.map((status) => (
      <div className="status" key={status.id}>
        {status.text}
      </div>
    )
  )}
</div>

This displays existing state. Your code needs to fetch statuses on page load.

Add a new method called fetchData() after the saveNewStatus() method.

fetchData() {
  const { userSession } = this.props
  this.setState({ isLoading: true })
  const options = { decrypt: false }
  userSession.getFile('statuses.json', options)
    .then((file) => {
      var statuses = JSON.parse(file || '[]')
      this.setState({
        person: new Person(userSession.loadUserData().profile),
        username: userSession.loadUserData().username,
        statusIndex: statuses.length,
        statuses: statuses,
      })
    })
    .finally(() => {
      this.setState({ isLoading: false })
    })
}

Call fetchData() from the componentDidMount() method.


componentDidMount() {
  this.fetchData()
}

Save the file.

After the application compiles successfully, users are able to Submit multiple statuses and review them in the app.

Change the style

Edit the src/styles/style.css file.

Replace the content with the following:

/* Globals */
a,a:focus,a:hover{color:#fff;}
html,body{height:100%;text-align:center;background-color:#191b22;}
body{color:#fff}
.hide{display:none;}
.landing-heading{font-family:'Lato',Sans-Serif;font-weight:400;}

/* Buttons */
.btn{font-family:'Lato',Sans-Serif;padding:0.5625rem 2.5rem;font-size:0.8125rem;font-weight:400;line-height:1.75rem;border-radius:0!important;-webkit-transition:all .2s ease-in-out;-moz-transition:all .2s ease-in-out;-ms-transition:all .2s ease-in-out;-o-transition:all .2s ease-in-out;transition:all .2s ease-in-out;-webkit-user-select:none;-moz-user-select:none;-ms-user-select:none;user-select:none;}
.btn-lg{font-size:1.5rem;padding:0.6875rem 3.4375rem;line-height:2.5rem;}
.btn:focus,.btn:active:focus,.btn.active:focus{outline:none;}
.btn-primary{color:#fff;border:1px solid #2C96FF;background-color:#2C96FF;}
.btn-primary:hover,.btn-primary:focus,.btn-primary:active{color:#fff;border:1px solid #1a6ec0;background-color:#1a6ec0;}

/* Avatar */
.avatar{width:100px;height:100px;}
.avatar-section{margin-bottom:25px;display:flex;text-align:left;}
.username{margin-left:20px;}

/* Scaffolding */
.site-wrapper{display:table;width:100%;height:100vh;min-height:100%;}
.site-wrapper-inner{display:flex;flex-direction:column;justify-content:center;margin-right:auto;margin-left:auto;width:100%;height:100vh;}
.panel-authed{padding:0 0 0 0;}

/* Home button */
.btn-home-hello{position:absolute;font-family:'Source Code Pro',monospace;font-size:11px;font-weight:400;color:rgba(255,255,255,0.85);top:15px;left:15px;padding:3px 20px;background-color:rgba(255,255,255,0.15);border-radius:6px;-webkit-box-shadow:0px 0px 20px 0px rgba(0,0,0,0.15);-moz-box-shadow:0px 0px 20px 0px rgba(0,0,0,0.15);box-shadow:0px 0px 20px 0px rgba(0,0,0,0.15);}

/* Input */
input, textarea{color:#000;padding:10px;}
.input-status{width:100%;height:70px;border-radius:6px;}
.new-status{text-align:right;}

/* Statuses */
.statuses{padding-top:30px;}
.status{margin:15px 0px;padding:20px;background-color:#2e2e2e;border-radius:6px}

Save and close the src/styles/style.css file.

After the application compiles, you should see the following:

At this point, you have a basic micro-blogging app that users can use to post and view statuses. However, there's no way to view other users' statuses. You'll add that in the next section.

Lookup user profiles

Let's now modify the Profile.js file to display profiles of other users. You'll be using the lookupProfile() method that you added to the import statement earlier. lookupProfile() takes a single parameter that is the Blockstack ID of the profile and returns a profile object.

Add a new route

Make some changes to the routing structure of your app so that users can view other users' profiles by visiting http://127.0.0.1:3000/other_user.id

Edit the src/components/App.js file.
Add the new route by importing the Switch and Route components from react-router-dom:
```
import { Switch, Route } from 'react-router-dom'
```

Locate this line below in the render() method:

: <Profile userSession={userSession} handleSignOut={ this.handleSignOut } />

Replace it with the following:

  :
  <Switch>
    <Route
      path='/:username?'
      render={
        routeProps => 
          <Profile 
            userSession={userSession} 
            handleSignOut={ this.handleSignOut } 
            {...routeProps} 
          />
      }
    />
  </Switch>

This sets up a route and captures the route path in the URL as the profile lookup username.

Save and close the the src/components/App.js file.

Add in lookupProfile

You also need to add a rule to your app's webpack config so that you can properly process URL paths that contain the . (dot) character for example, http://localhost:8080/other_user.id

NOTE: In a production app, you must ensure the web server is configured to handle this.

Open the src/components/Profile.js file.

Expand the import from blockstack statement to include the lookupProfile method.

Add lookupProfile after Person.

 When you are done, the import statement should look like the following:

import {
  Person,
  lookupProfile
} from 'blockstack';

Add a single method to the Profile class that determines if the app is viewing the local user's profile or another user's profile.
```
isLocal() {
  return this.props.match.params.username ? false : true
}
```
You use isLocal() to check if the user is viewing the local user profile or another user's profile. If it's the local user profile, the app runs the getFile() function you added in an earlier step. Otherwise, the app looks up the profile belonging to the username using the lookupProfile() method.

Modify the fetchData() method like so:

fetchData() {
  const { userSession } = this.props
  this.setState({ isLoading: true })
  if (this.isLocal()) {
    const options = { decrypt: false }
    userSession.getFile('statuses.json', options)
      .then((file) => {
        var statuses = JSON.parse(file || '[]')
        this.setState({
          person: new Person(userSession.loadUserData().profile),
          username: userSession.loadUserData().username,
          statusIndex: statuses.length,
          statuses: statuses,
        })
      })
      .finally(() => {
        this.setState({ isLoading: false })
      })
  } else {
    const username = this.props.match.params.username

    lookupProfile(username)
      .then((profile) => {
        this.setState({
          person: new Person(profile),
          username: username
        })
      })
      .catch((error) => {
        console.log('could not resolve profile')
      })
  }
}

NOTE: For https deployments, the default Blockstack Core API endpoint for name lookups should be changed to point to a core API served over https. Otherwise, name lookups fail due to browsers blocking mixed content. Refer to the Blockstack.js documentation for details.

Add the following block to fetchData() right after the call to lookupProfile(username)... catch((error)=>{..} block:

const options = { username: username, decrypt: false }
userSession.getFile('statuses.json', options)
  .then((file) => {
    var statuses = JSON.parse(file || '[]')
    this.setState({
      statusIndex: statuses.length,
      statuses: statuses
    })
  })
  .catch((error) => {
    console.log('could not fetch statuses')
  })
  .finally(() => {
    this.setState({ isLoading: false })
  })

This fetches the user statuses.

Finally, you must conditionally render the logout button, status input textbox, and submit button so they don't show up when viewing another user's profile.

Replace the render() method with the following:

render() {
const { handleSignOut, userSession } = this.props;
const { person } = this.state;
const { username } = this.state;

return (
  !userSession.isSignInPending() && person ?
  <div className="container">
    <div className="row">
      <div className="col-md-offset-3 col-md-6">
        <div className="col-md-12">
          <div className="avatar-section">
            <img
              src={ person.avatarUrl() ? person.avatarUrl() : avatarFallbackImage }
              className="img-rounded avatar"
              id="avatar-image"
            />
            <div className="username">
              <h1>
                <span id="heading-name">{ person.name() ? person.name()
                  : 'Nameless Person' }</span>
              </h1>
              <span>{username}</span>
              {this.isLocal() &&
                <span>
                  &nbsp;|&nbsp;
                  <a onClick={ handleSignOut.bind(this) }>(Logout)</a>
                </span>
              }
            </div>
          </div>
        </div>
        {this.isLocal() &&
          <div className="new-status">
            <div className="col-md-12">
              <textarea className="input-status"
                value={this.state.newStatus}
                onChange={e => this.handleNewStatusChange(e)}
                placeholder="What's on your mind?"
              />
            </div>
            <div className="col-md-12 text-right">
              <button
                className="btn btn-primary btn-lg"
                onClick={e => this.handleNewStatusSubmit(e)}
              >
                Submit
              </button>
            </div>
          </div>
        }
        <div className="col-md-12 statuses">
        {this.state.isLoading && <span>Loading...</span>}
        {this.state.statuses.map((status) => (
            <div className="status" key={status.id}>
              {status.text}
            </div>
            )
        )}
        </div>
      </div>
    </div>
  </div> : null
);
}

This checks to ensure that users are viewing their own profile, by wrapping the Logout button and inputs with the {isLocal() && ...} condition.

Put it all together

Stop the running application in terminal by sending a CTRL-C.
Restart the application so that the disabling of the . (dot) rule takes effect.
```
npm start
```
Point your browser to http://127.0.01:3000/your_username.id.blockstack to see the final application.

Wrapping up

Congratulations, you are all done! We hope you've enjoyed learning a bit more about Blockstack.

A few things to note, you'll notice that in our putFile() and getFile() calls, we chose not to encrypt/decrypt because our app is meant to share statuses publicly. By default, putFile() and getFile() will encrypt all data stored, making it unreadable by everyone except the logged in user.

Resources

Complete source code

Live demo

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