Flutter

This category contains topics explaining how to configure Bucketeer's Flutter SDK.

Flutter SDK Version (Beta)

The Flutter SDK is currently in its Beta stage.

If you find any issues or have suggestions for improvement, feel free to open an issue.
The SDK doesn't support Flutter Web yet. All contributions are welcome!

Getting started

Before starting, ensure that you follow the Getting Started guide.

Implementing dependency

Implement the dependency in your Pubspec file. Please refer to the SDK releases page to find the latest version.

Pubspec

dependencies:
  bucketeer_flutter_client_sdk: LATEST_VERSION

Importing client

Import the Bucketeer client into your application code.

Dart

import 'package:bucketeer_flutter_client_sdk/bucketeer_flutter_client_sdk.dart';

Configuring client

Configure the SDK config and user configuration.

info

The featureTag setting is the tag you configure when creating a Feature Flag. It will evaluate all the Feature Flags in the environment when it is not configured.

We strongly recommend using tags to speed up the evaluation process and reduce the cache size in the client.

All the settings in the example below are required.

Dart

final config = BKTConfigBuilder()
  .apiKey("YOUR_API_KEY")
  .apiEndpoint("YOUR_API_URL")
  .featureTag("YOUR_FEATURE_TAG")
  .appVersion("YOUR_APP_VERSION")
  .build();

final user = BKTUserBuilder
  .id("USER_ID")
  .customAttributes(YOUR_USER_ATTRIBUTES) /// optional Map<String, String>
  .build();

Custom configuration

Depending on your use, you may want to change the optional configurations available in the BKTConfigBuilder.

• pollingInterval - Minimum 60 seconds. Default is 10 minutes (In Milliseconds)
• backgroundPollingInterval - Minimum 20 minutes. Default is 1 hour (In Milliseconds)
• eventsFlushInterval - Minimum 60 seconds. Default is 60 seconds (In Milliseconds)
• eventsMaxQueueSize - Default is 50 events

note

The Bucketeer SDK doesn't save the user data. The Application must save and set it when initializing the client SDK.

Initializing client

Initialize the client by passing the configurations in the previous step.

Dart

await BKTClient.initialize(config: config, user: user);

Default timeout

The initialize process default timeout is 5 seconds.
Once initialization is finished, all the requests in the SDK use a timeout of 30 seconds.

If you want to use the feature flag on Splash or Main views, the SDK cache may be old or not exist and may not have enough time to fetch the variations from the Bucketeer server. In this case, we recommend using await in the initialize method. In addition, you can define a custom timeout.

Initialization Timeout error

During the initialization process, errors are not related to the initialization itself. Instead, they arise from a timeout request, indicating the variations data from the server weren't received. Therefore, the SDK will work as usual and update the variations in the next polling request.

Dart

/// It will unlock without waiting until the fetching variation process finishes
const int timeout = 2000; /// Default is 5 seconds (In milliseconds)
final result = await BKTClient.initialize(
    config: config, user: user, timeoutMillis: timeout);
if (result.isSuccess) {
  const client = BKTClient.instance;
  final showNewFeature = await client
      .boolVariation("YOUR_FEATURE_FLAG_ID", defaultValue: false);
  if (showNewFeature) {
    /// The Application code to show the new feature
  } else {
    /// The code to run if the feature is off
  }
} else {
  /// Handle the error when there is no cache or the cache is not updated
  if (result.asFailure.exception is BKTTimeoutException) {
    /// Handle timeout error
  } else {
    /// Anything else
  }
}

Polling

The initialize process immediately starts polling the latest evaluations from the Bucketeer server in the background using the interval pollingInterval configuration while the application is in the foreground state. When the application changes to the background state, it will use the backgroundPollingInterval configuration.

Polling retry behavior

The Bucketeer SDK regularly polls the latest evaluations from the server based on the pollingInterval parameter. By default, the pollingInterval is set to 10 minutes, but you can adjust it to suit your needs.

If a polling request fails, the SDK initiates a retry procedure. The SDK attempts a new polling request every minute up to 5 times. If all five retry attempts fail, the SDK sends a new polling request once the pollingInterval time elapses. The table below shows this scenario:

Polling Time	Retry Time	Request Status
10:00	-	Fail
-	10:01	Fail
-	10:02	Fail
-	10:03	Fail
-	10:04	Fail
-	10:05	Fail
10:10	-	Successful

The polling counter, which uses the pollingInterval information, resets in case of a successful retry. The table below shows the described scenario.

Polling Time	Retry Time	Request status
10:00	-	Fail
-	10:01	Successful
10:11	-	Successful

Supported features

Evaluating user

The variation method determines whether or not a feature flag is enabled for a specific user.
To check which variation a specific user will receive, you can use the client like below.

Dart

final showNewFeature =
    await client.boolVariation("YOUR_FEATURE_FLAG_ID", false);
if (showNewFeature) {
  /// The Application code to show the new feature
} else {
  /// The code to run if the feature is off
}

caution

In case the feature flag is missing in the SDK, it will return the default value.

Variation types

The Bucketeer SDK supports the following variation types.

Dart

Future<bool> boolVariation(String featureId, { required bool defaultValue });

Future<String> stringVariation(String featureId, { required String defaultValue });

Future<int> intVariation(String featureId, { required int defaultValue });

Future<double> doubleVariation(String featureId, { required double defaultValue });

Future<Map<String, dynamic>> jsonVariation(String featureId, { required Map<String, dynamic> defaultValue });

Updating user evaluations

Depending on the use case, you may need to ensure the evaluations in the SDK are up to date before requesting the variation.

The fetch method uses the following parameter. Make sure to wait for its completion.

• Timeout - Default is 30 seconds (In milliseconds)

Dart

/// It will unlock without waiting until the fetching variation process finishes
int timeout = 5000; /// Optional. Default is 30 seconds (In milliseconds)

final result = await client.fetchEvaluations(timeoutMillis: timeout);
if (result.isSuccess) {
  final showNewFeature = await client
      .boolVariation("YOUR_FEATURE_FLAG_ID", defaultValue: false);
  if (showNewFeature) {
    /// The Application code to show the new feature
  } else {
    /// The code to run if the feature is off
  }
} else {
  /// Handle the error when the cache is not updated
  if (result.asFailure.exception is BKTTimeoutException) {
    /// Handle timeout error
  } else {
    /// Anything else
  }
}

caution

Depending on the client network, it could take a few seconds until the SDK fetches the data from the server, so use this carefully.

You don't need to call this method manually in regular use because the SDK is polling the latest variations in the background.

Updating user evaluations in real-time

Bucketeer SDK supports FCM (Firebase Cloud Messaging).
Every time you change a feature flag on the admin console, Bucketeer will send a silent notification using the FCM V1 API to notify the client so that you can update the evaluations in real-time.

Before using

1. You need to register your FCM Service Account on the admin console. Check the Pushes section to learn how to do it.
2. This feature may not work if the end-user has the notification disabled.

Subscription Topic

When using the FCM integration, your applications must subscribe to Bucketeer's topic, so they can receive notifications.

The topic varies depending on the feature flag tag.
E.g.: bucketeer-<YOUR_FEATURE_FLAG_TAG>

The tag in the topic is the same tag used when initializing the client SDK.
If you have a flag using the flutter tag, the topic will be bucketeer-flutter.

Please be aware that the tag is case-sensitive.

Assuming you already have the FCM implementation in your application.

Dart

/// In order to receive notifications you must subscribe to the topic
void subscribeToTopic() {
  String tag = "flutter";
  String topic = "bucketeer-$tag";

  FirebaseMessaging.instance.subscribeToTopic(topic).then((_) {
    debugPrint("Subscribed successfully to $topic topic");
  }).catchError((error) {
    debugPrint("Failed to subscribed to $topic topic. Error: $error");
  });
}

FirebaseMessaging.onMessage.listen((RemoteMessage message) async {
  final isFeatureFlagUpdated = message.data["bucketeer_feature_flag_updated"]
    if (isFeatureFlagUpdated "true") {
      int timeout = 1000;
      const client = BKTClient.instance;
      final result = await client.fetchEvaluations(timeoutMillis: timeout);
      if (result.isSuccess) {
        final showNewFeature = await client
            .boolVariation("YOUR_FEATURE_FLAG_ID", defaultValue: false);
        if (showNewFeature) {
          /// The Application code to show the new feature
        } else {
          /// The code to run if the feature is off
        }
      } else {
        /// Handle the error when the cache is not updated
        if (result.asFailure.exception is BKTTimeoutException) {
          /// Handle timeout error
        } else {
          /// Anything else
        }
      }
    }
});

Reporting custom events

This method lets you save user actions in your application as events. You can connect these events to metrics in the experiments console UI.

In addition, you can pass a double value to the goal event. These values will sum and show as
Value total on the experiments console UI. This is useful if you have a goal event for tracking how much a user spent on your application buying items, etc.

Dart

final result = await client.track("YOUR_GOAL_ID", value: 10.50);
if (result.isSuccess) {
  /// The Application code to run after track custom event
} else {
  /// Handle the error
}

Flushing events

This method will send all pending analytics events to the Bucketeer server immediately. This process is asynchronous, so it returns before it is complete.

Dart

await client.flush();

note

In regular use, you don't need to call the flush method because the events are sent every 60 seconds in the background.

User attributes configuration

This feature will give you robust and granular control over what users can see on your application. You can add rules using these attributes on the console UI's feature flag's targeting tab. See more.

Dart

final attributes = {
  'app_version': '1.0.0',
  'os_version': '11.0.0',
  'device_model': 'pixel-5'
  'language': 'english',
  'genre': 'female'
};

final user = BKTUserBuilder()
  .id("USER_ID")
  .customAttributes(attributes)
  .build();

await BKTClient.initialize(config: config, user: user);

Updating user attributes

This method will update all the current user attributes. This is useful in case the user attributes update dynamically on the application after initializing the SDK.

Dart

final attributes = {
  'app_version': '1.0.1',
  'os_version': '11.0.0',
  'device_model': 'pixel-5'
  'language': 'english',
  'genre': 'female'
  'country': 'japan'
};

final result = await client.updateUserAttributes(attributes);
if (result.isSuccess) {
  /// The Application code to run after update the user attributes
} else {
   /// Handle the error
}

caution

This updating method will override the current data.

Getting user information

This method will return the current user configured in the SDK. This is useful when you want to check the current user id and attributes before updating them through updateUserAttributes.

Dart

final userResult = await client.currentUser();
if (userResult.isSuccess) {
  final user = userResult.asSuccess.data;
  /// The Application code to run after get the user
} else {
  /// Handle the error
}

Getting evaluation details

This method will return the evaluation details for a specific feature flag or will return null if the feature flag is missing in the SDK's cache.

This is useful if you use another A/B Test solution with Bucketeer and need to know the variation name, reason, and other information.

Evaluation details

Dart

class BKTEvaluation {
  final String id;
  final String featureId;
  final int featureVersion;
  final String userId;
  final String variationId;
  final String variationName;
  final String variationValue;
  final String reason;
}

caution

Do not call this method without calling the Evaluating user method. The Evaluating user method must always be called because it generates analytics events that will be sent to the server.

Dart

final evaluationDetails = await client.evaluationDetails("YOUR_FEATURE_FLAG_ID");

Listening to evaluation updates

The SDK can notify when the evaluation is updated. The listener can detect both automatic polling and manual fetching.

Dart

class EvaluationUpdateListenerImpl implements BKTEvaluationUpdateListener {
  @override
  void onUpdate() async {
    const client = BKTClient.instance;
    final showNewFeature =
        await client.boolVariation("YOUR_FEATURE_FLAG_ID", defaultValue: false);
    if (showNewFeature) {
      /// The Application code to show the new feature
    } else {
      /// The code to run when the feature is off
    }
  }
}

final listener = EvaluationUpdateListenerImpl();
const client = BKTClient.instance;
/// The returned key value is used to remove the listener
final key = await client.addEvaluationUpdateListener(listener);
/// Remove a listener associated with the key
client.removeEvaluationUpdateListener(key);
/// Remove all listeners
client.clearEvaluationUpdateListeners();

Background mode

For Android, the background mode works without any configuration by default.
For iOS, this feature is optional, but it can be used by configuring the background mode in the Xcode project.
The default setting is 1 hour and a minimum of 20 minutes for the backgroundPollingInterval, and 1 minute for the eventsFlushInterval settings.

Configuration for iOS

1. Open the iOS folder using Xcode IDE to open the file Runner.xcworkspace.
2. Open the XCode project setting.
3. Select the Runner target.
4. Select the Signing & Capabilities settings tab.
5. Enable the Background processing option in the Background Modes section.
6. Register the identifier by adding the Permitted background task scheduler identifiers option in the Info.plist, and set the following task IDs as the values.

• io.bucketeer.background.fetch.evaluations (Background task to fetch the latest evaluations from the server).
• io.bucketeer.background.flush.events (Background task to flush events generated by the client).

7. Open the AppDelegate.swift and add the following code to the didFinishLaunchingWithOptions function.

import UIKit
import Bucketeer

class AppDelegate: UIResponder, UIApplicationDelegate {

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Add the code to enable background tasks
        if #available(iOS 13.0, tvOS 13.0, *) {
            BKTBackgroundTask.enable()
        }
        // Your app logic code
        return true
    }

8. If needed, change the background polling default interval by adding the backgroundPollingInterval setting in the BKTConfigBuilder as follows:

final config = BKTConfigBuilder()
  .apiKey("YOUR_API_KEY")
  .apiEndpoint("YOUR_API_URL")
  .featureTag("YOUR_FEATURE_TAG")
  .appVersion("YOUR_APP_VERSION").
  .eventsFlushInterval(60) /// 1 minute
  .backgroundPollingInterval(1800)
  .build(); /// 30 minutes

9. Please check the iOS Documentation for more details.

Destroying client

There are cases you might want to switch the user ID or reduce resources when the application is in the background.
For those cases, you can call the destroy interface, which will clear the client instance.

Dart

await client.destroy()

tip

If you want to switch the user ID, please call the flush interface before calling the destroy, so that all the pending events can be sent before clearing the client instance, then call the initialize interface with the new user information.