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User Authentication Basics

Introduction

Skygear user authentication is a collection of APIs that helps you manage users in your app.

Skygear stores and manages the user credentials internally and handles the user login session using an access token stored in the local storage.

The following diagram shows the login flow:

    +-------------------------------------+
    |        Initial page load and        |
    |     Skygear container configured    |
    +-------------------------------------+

                      |
                      |
                      v

    +-------------------------------------+
    |   1. Check if authenticated user    |
    |      exists in local storage        |
    +-------------------------------------+

                      |
                      |
          +-----------+-----------+
          |                       |
   2. No  |                       |  3. Yes
          |                       |
          v                       v

+-------------------+   +---------------------+
|  Anonymous state  |   |   Logged-in state   |
| (no access token) |   | (with access token) |
+-------------------+   +---------------------+

  ^   |                                 ^   |
  |   |    4. login/sign-up success     |   |
  |   +---------------------------------+   |
  |                                         |
  +-----------------------------------------+
   5. logout success or access token expired
  1. When the container is configured with the server endpoint and the API key, it will check for the existence of an authenticated user in the local storage.
  2. If there is none, the SDK will do nothing, the app remains in the anonymous state. There is no access token.
  3. If there is, the SDK will retrieve the user information, including the user record (email, username, etc.) and the access token.
  4. When a user logs in or signs up successfully, the SDK will set the user information with the access token obtained from the Skygear server. The app will change from the anonymous state to the logged-in state. The access token is sent to the server for authentication in every API call made through the SDK.
  5. When a user logs out of the access token is found expired during an API call to the server, the SDK will clear the user information and the access token. The app will change from the logged-in state to the anonymous state.

Signing up

Signing up with email or username

A user can sign up using a username or an email, along with a password. It is done using either skygear.auth.signupWithUsername or skygear.auth.signupWithEmail.

Skygear does not allow duplicated usernames or emails. Signing up with a duplicated identifier will give the error Duplicated.

While each of the sign-up functions is resolved with a user record, in most cases you need not deal with it because you can access the currently logged-in user using [skygear.auth.currentUser].

signupWithUsername sample code:

import skygear from 'skygear';

skygear.auth.signupWithUsername(username, password).then((user) => {
  console.log(user); // user record
  console.log(user["username"]); // username of the user
}, (error) => {
  console.error(error);
  if (error.error.code === skygear.ErrorCodes.Duplicated) {
    // the username has already existed
  } else {
    // other kinds of error
  }
});

signupWithEmail sample code:

import skygear from 'skygear';

skygear.auth.signupWithEmail(email, password).then((user) => {
  console.log(user); // user record
  console.log(user["email"]); // email of the user
}, (error) => {
  console.error(error);
  if (error.error.code === skygear.ErrorCodes.Duplicated) {
    // the email has already existed
  } else {
    // other kinds of error
  }
});

It is common to add other data to user record when signing up, you can do that by specifying the data for user record in the third parameter of the signup functions:

import skygear from 'skygear';

var otherData = { "interest": "reading" };

// sign up with email and also add data to user record
// this also work for signupWithUsername
skygear.auth.signupWithEmail(email, password, otherData).then((user) => {
  console.log(user["interest"]); // print "reading"
}, (error) => {
  console.error(error);
});

Signing up anonymously

Without being authenticated, a user can read data from the public database but cannot perform most of the other operations, including saving data into the database.

If you need an authenticated user but do not require a user to sign up explicitly with a username or email, you can create an anonymous user by calling skygear.auth.signupAnonymously.

Every anonymous user has a unique user ID, and behaves exactly the same as any user authenticated with a username or an email. The only difference is that an anonymous user has no username, email, nor password. Because of the absence of username and email, the account will be lost when the access token is lost.

import skygear from 'skygear';

skygear.auth.signupAnonymously().then((user) => {
  console.log(user); // user record without email and username
}, (error) => {
  console.error(error);
});

Logging in

The login functions are similar to the sign-up ones.

If the credentials are incorrect, it will give the error of:

  • InvalidCredentials if the password is incorrect;
  • ResourceNotFound if the email or username is not found.

While each of the login functions is resolved with a user record, in most cases you need not deal with it because you can access the currently logged-in user using [skygear.auth.currentUser].

Logging in using a username

skygear.auth.loginWithUsername(username, password).then((user) => {
  console.log(user); // user record
}, (error) => {
  console.error(error);
  if (error.error.code === skygear.ErrorCodes.InvalidCredentials ||
      error.error.code === skygear.ErrorCodes.ResourceNotFound ) {
    // incorrect username or password
  } else {
    // other kinds of error
  }
})

Logging in using an email

skygear.auth.loginWithEmail(email, password).then((user) => {
  console.log(user); // user record
}, (error) => {
  console.error(error);
  if (error.error.code === skygear.ErrorCodes.InvalidCredentials ||
      error.error.code === skygear.ErrorCodes.ResourceNotFound ) {
    // incorrect email or password
  } else {
    // other kinds of error
  }
})

Logging out

Logging out the current user is simple using the skygear.auth.logout method.

Upon successful logout, the SDK will clear the current user and the access token from the local storage.

skygear.auth.logout().then(() => {
  console.log('logout successfully');
}, (error) => {
  console.error(error);
});

Getting the current user

You can retrieve the current user from [skygear.auth.currentUser].

const user = skygear.auth.currentUser; // if not logged in, it will be null

If there is an authenticated user, it will give you a Record which is the user record. The user record looks like this:

{
  '_id': 'abcdef',
  'username': 'Ben',
  'email': 'ben@skygeario.com',
}

Please be reminded that the currentUser object persist locally, and the data in the user record might not sync with the server if it was changed remotely.

To get the latest information of the current user, you can call whoami:

skygear.auth.whoami().then((user) => {
    console.log(`Oh. I am ${user.username}.`);
}, (err) => {
    // Error handling...
})

Observing user changes

The preferred way for your app to handle any logged-in user change is to register a callback by using the skygear.auth.onUserChanged method. The callback will be invoked whenever the user is changed, i.e. when any of the followings happens:

  1. a user logs in;
  2. a user logs out (or as logged out due to an expired access token);

The callback will receive the new user record as the argument.

const handler = skygear.auth.onUserChanged(function (user) {
  if (user) {
    console.log('user logged in or signed up');
  } else {
    console.log('user logged out or the access token expired');
  }
});

handler.cancel(); // The callback is cancelable

Updating a user's username and email

Username and email is saved to the user record. You can modify the username and email in the same way you modify any other record, which is achieved by calling [skygear.publicDB.save].

Caution: When saving user record, the user record returned by currentUser is not automatically updated. To force an update of the record returned from currentUser, call whoami.

To change the username of the current user:

var user = skygear.auth.currentUser;
user["username"] = "new-username"
skygear.publicDB.save(user).then((user) => {
  console.log(user); // updated user record
  console.log('Username is changed to: ', user["username"]);
  return skygear.auth.whoami();
}, (error) => {
  console.error(error);
});

To change the email of the current user:

var user = skygear.auth.currentUser;
user["email"] = "new-email@example.com"
skygear.publicDB.save(user).then((user) => {
  console.log(user); // updated user record
  console.log('Email is changed to: ', user["email"]);
  return skygear.auth.whoami();
}, (error) => {
  console.error(error);
});

You can even change the username and email at the same time:

var user = skygear.auth.currentUser;
user["username"] = "new-username"
user["email"] = "new-email@example.com"
skygear.publicDB.save(user).then((user) => {
  console.log(user); // updated user record
}, (error) => {
  console.error(error);
});

Updating a user's password

The currently logged-in user can change his/her own password. This can be done using the skygear.auth.changePassword function.

If the current password is incorrect, the SDK will return an InvalidCredentials error.

skygear.auth.changePassword(currentPassword, newPassword).then((user) => {
  console.log(user); // user record
  console.log('Password has been changed');
}, (error) => {
  console.error(error);
  if (error.error.code === skygear.ErrorCodes.InvalidCredentials) {
    // the current password is incorrect
  } else {
    // other kinds of error
  }
});

Note: Changing the password of the current user will not trigger the callback registered through skygear.auth.onUserChanged.

Invalidating existing access tokens

If you are using the JWT token store, all existing access tokens will be invalidated when a user changes his/her password.

[Not yet implemented] If you are not using the JWT token store, you can invalidate existing tokens by setting invalidate to true:

skygear.auth.changePassword(currentPassword, newPassword, invalidate=true)
.then((user) => {
  console.log(user); // user object
  console.log('The user has got a new access token');
}, (error) => {
  console.error(error);
});

Forgot password

Coming soon.

User Verification

Not yet implemented.

What's next from here?

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