Contact collections. This release allows developers to try out the new collections functionality and we are interested in collecting feedback. Please feel free to report issues or request enhancements with collections or Contacts themselves on the blockstack/blockstack-collections repository. If you encounter problems with blockstack.js you can file issues or request enhancements on its repo." %}
## Understand how collections work
One of Blockstack's goals is to give users true data ownership by enabling *data portability*. Data portability allows users to login with their digital ID on any app and have access to the same data. For example, if a user adds a photo of a Hawaiian vacation in one app, that photo enters the user's data pool. Then, when the user opens a second app, that same photo is available to the second app because the user data, including the photo, is shared via the user's decentralized ID.
How do collections work? Blockstack builds a library containing commonly used data schemes. Developers use these classes and objects instead of creating their own, unique data schemes. Using a class from the collections library guarantees class data is stored in Gaia in that format; And, when retrieved, guarantees the same format is returned. This pre-release provides the `Contact` collection. A contact schema produces this structure:
```
{
"lastName": "jeffries",
"firstName": "sally",
"blockstackID": "",
"email": "",
"website": "",
"telephone": "",
"identifier": "sally jeffries"
}
```
A collection schema is neither validated or enforced. The goal is to incentivize collection use rather that enforce use.
Because malicious apps or apps with poor security controls may damage user data, Blockstack believes collections should include the ability for users to roll-back changes. For this reason, Blockstack supports an event log and rollback mechanisms in collections. To support this rollback in the pre-release, collections data store is conceptually an event log. Every data write an app makes is stored as a separate file. By placing data in files it ensures that data is never lost and files can be returned back to any previous state.
Blockstack believes that collections should enable true data portability across applications for each decentralized ID. The goal is to develop simple user interfaces to allow users to manage of application access and permissions to collection data. For example, in the future, users can rollback data to previous versions using management interfaces.
For developers, collections can incentivize user adoption by reducing user friction. Users can easily try new apps and move to them without the overhead or barrier of re-entering data. You are welcome to review and comment on the current design document.
https://staging-hub.blockstack.xyz Gaia hub during the Contact Manager onboarding. For this reason, wait to create a new ID." %}
4. Go to the local Blockstack Browser and make sure you see this:
Do not create an ID yet.
5. In your Internet browser, visit the https://github.com/yknl/blockstack-contacts repository.
6. Download or clone the repository code to you local workstation.
7. In your workstation terminal, change directory where you downloaded the demo code.
8. Install the dependencies using `npm`.
```bash
npm install
```
9. Start the application running.
```bash
npm run start
```
The system starts the application and launches it in your browser at 127.0.0.1:3000
10. Choose **Sign In with Blockstack**.
This system displays this pop-up
11. Use the local browser by choosing **Open Blockstack.app**.
12. Choose **Create new ID** from the pop up.
The onboarding should prompt you to store your data with the `https://staging-hub.blockstack.xyz` provider.
13. Choose **Yes, use the recommended provider** and complete the creation of your test ID.
The system should return you to the Contact Manager demo application.
Try adding a contact using the Contact Manager. When you have successfully created a contact, the Contact Manager displays that contact on the list. Here you can see that Alfred Newman was entered as a contact.
## How to add the Contact collections to your DApp
In this section, you learn how to add `Contact` collection functionality to an existing application. Before beginning, make sure your application is using Blockstack auth and is storing data with Gaia. To start using the `Contact` collection in your Blockstack app, do the following:
1. Change to the root directory of your app project.
2. Install the preview branch of the `blockstack.js`.
```
npm install blockstack@20.0.0-alpha.4
```
3. Add the ``blockstack-collections` package to your app.
```
npm install blockstack-collections@0.1.8
```
4. Edit your code to import the `Contact` collection type.
```
import { Contact } from `blockstack-collections`
```
5. Customize your sign in request to include the contacts collection scope `Contact.scope`.
This scope grants your app permission to read and write to the user’s `Contacts` collection.
```javascript
import { UserSession, AppConfig, makeAuthRequest } from 'blockstack'
import { Contact } from '`blockstack-collections'
const scopes = ['store_write', 'publish_data', Contact.scope]
const appConfig = new AppConfig(scopes)
const userSession = new UserSession({appConfig: appConfig})
const authRequest = makeAuthRequest(undefined, undefined, undefined, scopes, undefined, undefined, {
solicitGaiaHubUrl: true,
recommendedGaiaHubUrl: 'https://staging-hub.blockstack.xyz'
})
userSession.redirectToSignInWithAuthRequest(authRequest)
```
{% include note.html content="This example enables the custom Gaia hub selection prompt to point at the pre-release hub that has collections features enabled." %}
## Collection storage operations
Collection storage was designed around an ORM-like interface. This approach ensures that you’ll be working with typed objects instead of the `getFile`, `putFile` functions provided by blockstack.js.
### Example: Create and save a Contact object
```javascript
const newContact = {
lastName: 'Stackerson',
firstName: 'Blocky',
blockstackID: 'Blockstacker.id',
email: 'blockstacker@blockstack.org',
website: 'blockstack.org',
telephone: '123123123'
}
var contact = new Contact(newContact)
contact.save().then((contactID) => {
// contact saved successfully
})
```
### Example: Read a Contact object
```javascript
let contactID = 'Blocky Stackerson'
Contact.get(contactID).then((contact) => {
// Do something with the contact object
console.log('Hello ${contact.firstName}')
})
```
### Example: List Contact objects
```javascript
let contacts = []
Contact.list((contactID) => {
// This callback is invoked for each contact identifier
// To get the actual object you'll need to use Contact.get
// Or you can add the IDs to an array for display
contacts.push(contactID)
// Return true to continue iterating, return false to stop
return true
})
```
### Example: Delete a Contact
```javascript
var contact = new Contact(newContact)
contact.delete().then(() => {
// contact deleted successfully
})
```