How do I link each user to their data in Firebase?

Question

I plan to create a main tree named users which will include the name different users used as username. So, from each username will be included their data eg Full Name, Address, Phone No.

I want to know how to get each user's data when they log in on their profile.

Answer 1

First of all i suggest you spend some time getting familiar with firebase by reading the Firebase Guide ( Link to old Firebase Guide ). Everything you need to know to answer your own question is available there. But for simplicity i will put an example here:

Lets start with security, here are the basic firebase rules you need for this example: (source: Understanding Security ) (old source: Understanding Security )

{
  "rules": {
    "users": {
      "$user_id": {
        ".write": "$user_id === auth.uid"
      }
    }
  }
}

I will skip the actual user creation and logging in and focus on the question about storing and retrieving user data.

Storing data: (source: Firebase Authentication ) (old source: User Authentication )

// Get a reference to the database service
var database = firebase.database();
// save the user's profile into Firebase so we can list users,
// use them in Security and Firebase Rules, and show profiles
function writeUserData(userId, name, email, imageUrl) {
  firebase.database().ref('users/' + userId).set({
    username: name,
    email: email
    //some more user data
  });
}

The resulting firebase data will look like this:

{
  "users": {
    "simplelogin:213": {
      "username": "password",
      "email": "bobtony"
    },
    "twitter:123": {
      "username": "twitter",
      "email": "Andrew Lee"
    },
    "facebook:456": {
      "username": "facebook",
      "email": "James Tamplin"
    }
  }
}

And last but not least the retreiving of the data, this can be done in several ways but for this example i'm gonna use a simple example from the firebase guide: (source: Read and Write data ) (old source: Retreiving Data )

//Get the current userID
var userId = firebase.auth().currentUser.uid;
//Get the user data
return firebase.database().ref('/users/' + userId).once('value').then(function(snapshot) {
    //Do something with your user data located in snapshot
});

EDIT: Added example of return data

So when you are logged in as user twitter:123 you will get a reference to the location based on your user id and will get this data:

"twitter:123": {
          "username": "twitter",
          "email": "Andrew Lee"
        }

Answer 2

Though I agree with Andre about setting the rules for good security - I would handle the data a bit differently. Instead of generating the string I use the child() method. It's a matter of personal preference.

Get the UID and define a data object:

let user = firebase.auth().currentUser
let uid = user.uid
let yourdata = { foo: 'something', bar: 'other'}

Save the data:

firebase.database().ref('users').child(uid).set(yourdata)
    .then((data) => {
        console.log('Saved Data', data)
    })
    .catch((error) => {
        console.log('Storing Error', error)
    })    

Fetch the data:

firebase.database().ref('users').child(uid).once('value')
    .then((data) => {
        let fetchedData = data.val()
        console.log('Fetched Data', fetchedData)
    })
    .catch((error) => {
        console.log('Fetching Error', error)
    })    

Please notice that set() will override your data so you might want to use push() later on.