You can use Firebase Authentication to create and use temporary anonymous accounts
to authenticate with Firebase. These temporary anonymous accounts can be used to
allow users who haven't yet signed up to your app to work with data protected
by security rules. If an anonymous user decides to sign up to your app, you can
link their sign-in credentials to the anonymous
account
so that they can continue to work with their protected data in
future sessions.
Before you begin
- Add Firebase to your C++
project
.
- If you haven't yet connected your app to your Firebase project, do so from
the
Firebase console
.
- Enable anonymous auth:
- In the
Firebase console
, open the
Auth
section.
- On the
Sign-in Methods
page, enable the
Anonymous
sign-in method.
- Optional
: If you've upgraded your project to
Firebase Authentication with Identity Platform
, you can enable automatic clean-up. When
you enable this setting, anonymous accounts older than 30 days will be automatically
deleted. In projects with automatic clean-up enabled, anonymous authentication will no
longer count toward usage limits or billing quotas. See
Automatic clean-up
.
Authenticate with Firebase anonymously
When a signed-out user uses an app feature that requires authentication with
Firebase, sign in the user anonymously by completing the following steps:
The
Auth
class is the gateway for all API calls.
- Add the Auth and App header files:
#include "firebase/app.h"
#include "firebase/auth.h"
- In your initialization code, create a
firebase::App
class.
#if defined(__ANDROID__)
firebase::App* app =
firebase::App::Create(firebase::AppOptions(), my_jni_env, my_activity);
#else
firebase::App* app = firebase::App::Create(firebase::AppOptions());
#endif // defined(__ANDROID__)
- Acquire the
firebase::auth::Auth
class for your
firebase::App
.
There is a one-to-one mapping between
App
and
Auth
.
firebase::auth::Auth* auth = firebase::auth::Auth::GetAuth(app);
Call
Auth::SignInAnonymously
.
firebase::Future<firebase::auth::AuthResult> result =
auth->SignInAnonymously();
If your program has an update loop that runs regularly (say at 30 or 60
times per second), you can check the results once per update with
Auth::SignInAnonymouslyLastResult
:
firebase::Future<firebase::auth::AuthResult> result =
auth->SignInAnonymouslyLastResult();
if (result.status() == firebase::kFutureStatusComplete) {
if (result.error() == firebase::auth::kAuthErrorNone) {
firebase::auth::AuthResult auth_result = *result.result();
printf("Sign in succeeded for `%s`\n",
auth_result.user.display_name().c_str());
} else {
printf("Sign in failed with error '%s'\n", result.error_message());
}
}
Or, if your program is event driven, you may prefer to
register a callback on the
Future
.
Convert an anonymous account to a permanent account
When an anonymous user signs up to your app, you might want to allow them to
continue their work with their new account—for example, you might want to
make the items the user added to their shopping cart before they signed up
available in their new account's shopping cart. To do so, complete the following
steps:
- When the user signs up, complete the sign-in flow for the user's
authentication provider up to, but not including, calling one of the
Auth::SignInWith
methods. For example, get the user's Google ID token,
Facebook access token, or email address and password.
Get an
auth::Credential
for the new authentication provider:
Google Sign-In
firebase::auth::Credential credential =
firebase::auth::GoogleAuthProvider::GetCredential(google_id_token,
nullptr);
Facebook Login
firebase::auth::Credential credential =
firebase::auth::FacebookAuthProvider::GetCredential(access_token);
Email-password sign-in
firebase::auth::Credential credential =
firebase::auth::EmailAuthProvider::GetCredential(email, password);
Pass the
auth::Credential
object to the sign-in user's
LinkWithCredential
method:
// Link the new credential to the currently active user.
firebase::auth::User current_user = auth->current_user();
firebase::Future<firebase::auth::AuthResult> result =
current_user.LinkWithCredential(credential);
If the call to
LinkWithCredential
succeeds, the user's new account can
access the anonymous account's Firebase data.
Automatic clean-up
If you've upgraded your project to
Firebase Authentication with Identity Platform
, you can
enable automatic clean-up in the Firebase console. When you enable this feature you allow
Firebase to automatically delete anonymous accounts older than 30 days. In projects with automatic
clean-up enabled, anonymous authentication will not count toward usage limits or billing quotas.
- Any anonymous accounts created after enabling automatic clean-up might be automatically
deleted any time after 30 days post-creation.
- Existing anonymous accounts will be eligible for automatic deletion 30 days after
enabling automatic clean-up.
- If you turn automatic clean-up off, any anonymous accounts scheduled to be deleted will remain
scheduled to be deleted.
- If you "upgrade" an anonymous account by linking it to any sign-in method, the account will
not get automatically deleted.
If you want to see how many users will be affected before you enable this feature, and you've
upgraded your project to
Firebase Authentication with Identity Platform
, you can filter by
is_anon
in
Cloud
Logging
.
Next steps
Now that users can authenticate with Firebase, you can control their access to
data in your Firebase database using
Firebase rules
.