Description of A/B testing on the SDK side

Step 1

Some operations can take a while because the SDK operates asynchronously. These operations are:

A/B test configuration.

After you’ve created an A/B test in the web interface, the SDK will receive its configuration via the network. Use the remoteConfigWaiting property in the DTDRemoteConfig class to set the maximum time allowed for waiting for the A/B test configuration.

remoteConfigWaitingis set in seconds

By default, the remoteConfigWaiting value is equal to null. This means that the test configuration waiting time is unlimited. The limitation is important in case the test that you are about to execute can influence your app functioning.

Example: DTDRemoteConfig.remoteConfigWaiting = 10

In this case, the SDK will wait for the A/B test configuration for 10 seconds. If it won’t receive the config during the allocated time, it will notify the developer by using the onReceived(result: DTDRemoteConfigReceiveResult) method with Failure value and disable the A/B testing until the next SDK initialization.

Waiting for an A/B test group.

After the SDK finds a test, it will wait for a suitable group to include the user into and start the experiment.

By default, waiting time (groupDefinitionWaiting) is 10 seconds.

You can change this value up or down.

Example: DTDRemoteConfig.groupDefinitionWaiting = 15

In this case, the SDK will wait for a group for no more than 15 seconds. If It can't find a suitable test for 15 seconds, it will be cancelled and its activation will be impossible. After the next SDK initialization (app restart), the user will have another chance to participate in the test.

The DTDRemoteConfig.remoteConfigWaiting and DTDRemoteConfig.groupDefinitionWaitingvalues can be set only prior to SDK initialization!

Step 2

In the DTDRemoteConfig class you need to set the default variables and their values using the DTDRemoteConfig.defaults property.

The variable values in the defaults property do not change on the SDK side.

After setting up DTDRemoteConfig.defaults, you can receive the variable values by using the DTDRemoteConfig.config property.

When working with A/B tests, always use the config property to receive the actual variables and their values!

If for some reasons, the device can not be included in the test (no network or network problems, devtodev did not assign it to a group, incorrect SDK implementation, etc.) DTDRemoteConfig.config will return default values. Using this approach, you can always shape the desirable UI and the business logic of the app.

Step 3

To work with A/B testing, use the DTDAnalytics.initializeWithAbTest initialization method.

If you used DTDAnalytics.initialize previously, you need to replace it with DTDAnalytics.initializeWithAbTest as the SDK initialization method.

The DTDRemoteConfigListener interface is added to the initializeWithAbTest method. It implements three methods:

  • onReceived(result: DTDRemoteConfigReceiveResult)

  • onPrepareToChange()

  • onChanged(result: DTDRemoteConfigChangeResult, error: Error?)

The DTDRemoteConfigListenermethods are not called in the main thread - you need to keep this in mind when interacting with UI elements of the app. Also, do not execute operations that block the thread in the DTDRemoteConfigListener methods, because this will disable the SDK operation (see examples).

Step 4

Methods implementation for working with A/B tests. When suitable conditions for the test occur, the following chain of events gets initiated:

  • Calling onReceived method

  • Calling onPrepareToChange method

  • Calling onChanged method


The onReceived method is triggered every time when the SDK loads A/B test configuration. The result argument returns the following:

  • Success if the configuration was loaded in the time provided. Time is set by the user in DTDRemoteConfig.remoteConfigWaiting.

  • Failure if the config wasn’t received during the provided time defined by the user in DTDRemoteConfig.remoteConfigWaiting.

  • Empty if the configuration was loaded in the time provided, but the list of experiments is empty. Time is set by the user in DTDRemoteConfig.remoteConfigWaiting.

If the DTDRemoteConfig.remoteConfigWaiting’s default value is equal to null, the OnReceived method and DTDRemoteConfigReceiveResult.Success are called when the config is received. The time of the OnReceived call depends on the network speed.


The onPrepareToChange() method is designed to notify the developer that the configuration of the A/B tests will be changed (the test is found or canceled, switch to a user who is not participating in the experiment, etc. (see Some features in the behavior of interfaces)).

SDK asynchronous behavior causes a gap in time between the moment the suitable conditions for the test occur and its possible activation. You need to keep this in mind when changing the app’s UI and UX and pause the user’s interaction with the app until it comes into action:

  • onChanged (see onChanged description) and a decision on test participation with a new config is made (see applyConfig description).

  • A timer on the developer’s side. The timer defines the time allocated for new config waiting. After the time has run out, waiting for the config should be canceled.

See the implementation example (Scenario 1)

After calling onPrepareToChange, the SDK executes an asynchronous request for entering the test. That will result in calling onChanged.

In case of disruption of the Internet connection or loss of focus, the test will be considered canceled until the next app launch.


The onChanged method is triggered in one of the following cases:

  • The DevToDev server offers to enroll in a test. onChanged() with DTDRemoteConfigChangeResult.success is called

  • The DevToDev server refuses to execute the test. onChanged() with DTDRemoteConfigChangeResult.failure is called

  • The device has no internet connection. onChanged() with DTDRemoteConfigChangeResult.failure is called

  • If the offer is received after the 30 second waiting time has expired onChanged() with DTDRemoteConfigChangeResult.failure is called

  • The test was previously activated (during the initialization) onChanged() with DTDRemoteConfigChangeResult.success is called

If the onChanged method is triggered with status == DTDRemoteConfigChangeResult.success value, the possible options are:

  • Accept the configuration by calling the DTDRemoteConfig.applyConfig() method If the configuration is accepted, the default parameters and group parameters (issued by the server) will overlap. After that, the parameters of the new configuration will be available in DTDRemoteConfig.config (you can use them to change the behavior or the interface of the app).

  • Refuse enrollment in the test DTDRemoteConfig.resetConfig() If the test enrollment is refused or the time for decision making is up, the SDK will temporarily flag the test and it will become unavailable until the next initialization. After the next initialization, the test will be available for participation when its requirements are fulfilled.

In the cases where status == DTDRemoteConfigChangeResult.failure, the DTDRemoteConfig.applyConfig() method will be triggered and the default configuration will stay in place.

Examples of SDK integration intended for working with A/B tests

Set the default values DTDRemoteConfig.defaults = ["button_color": "green", "button_size": "8"]

Variable names have to be the same as in the ‘Group settings’ section of the web interface (see ‘web’ above). When the SDK gets included in the A/B test, the devtodev server automatically assigns it to a group.

SDK will not use new variable values that are not set in DTDRemoteConfig.defaults

Example of the DTDRemoteConfig.configvalue variants:

Key/Valuedefaults Control Group Group A Group B











Example of SDK initialization that includes A/B testing:

import UIKit
import DTDAnalytics

class AppDelegate: UIResponder, UIApplicationDelegate, DTDRemoteConfigListener {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Config timeout, optional
        DTDRemoteConfig.remoteConfigWaiting = 10.0
        // Group timeout, optional
        DTDRemoteConfig.groupDefinitionWaiting = 15.0
        // Implementation defaults params
        DTDRemoteConfig.defaults = ["button_color": "green",
                                    "button_size": "8"]
        // Initialize SDK with ab test
        DTDAnalytics.initializeWithAbTest(applicationKey: "appKey",
                                          abConfigListener: self)
        return true

    // The method is called when the configuration has been received
    func onReceived(result: DTDRemoteConfigReceiveResult) {
        print("Configuration received, result \(result)")

    // Called when experiment is found
    func onPrepareToChange() {
        print("Experiment found")

    // Called when SDK receives config
    func onChanged(result: DTDRemoteConfigChangeResult, error: Error?) {
        print("DTDRemoteConfigChangeResult: \(result)")
        if let error = error {
            print("DTDRemoteConfigError: \(error.localizedDescription)")
        // Use here or notify config listeners that actualConfig is ready
        let btnColorRemoteValue = DTDRemoteConfig.config["button_color"].stringValue
        let btnSizeRemoteValue = DTDRemoteConfig.config["button_size"].stringValue
        print("button color: \(btnColorRemoteValue)")
        print("button size: \(btnSizeRemoteValue)")

Some features of A/B testing

When the SDK finds a suitable test(s), it calls the onPrepareToChange method and reports it. Then the SDK starts a timer for 30 seconds and sends a request to the devtodev server. The server returns an experiment number and information about a group. Or the server answers that the user can not participate in the test. This process takes some time. The request and answer can take as little as milliseconds, or much longer (30 seconds maximum) if, for example, the device’s internet connection is bad. Below, you can find several use cases that may help you to solve this problem if your app’s interface is sensitive to waiting for the config from devtodev.

Description of external interfaces


When working with this class, the SDK provides synchronization of threads that aims at providing safe operation taking into account the asynchrony of the SDK.


remoteConfigWaiting: Double

Wait time for A/B test configuration.

Default value - 0.0 (measured in seconds)

groupDefinitionWaiting: Double

Wait time for test group.

Default value - 10.0 (measured in seconds)

defaults: [String, Any]

Variables and their default values

config: DTDRemoteConfigCollection

Wrapper for remote parameters in the form of a collection. It allows access to the configuration values by using the subscripting syntaxis.

Actual variables and their values for working with A/B tests


It applies the A/B testing configuration. After the call, the default parameters get matched with the group parameters.


It cancels a suitable or running test


A debug method for saving a test experiment after restarting the application


Wrapper for remote parameters collection. Enables access to configuration values by using subscripting syntax.


hasKey(key: String)

Return true if current configuration has value for a key.


Wrapper for working with remote configuration variables. It represents a method for data source identification, as well as methods for presenting values in the form of various data types.



The variable is set by default.


The variable is set by the test group.


The variable is not found in the remote configuration.




Gets the value as an optional string.



Gets the value as a Float.



Gets the value as a Double.



Gets the value as an Int32.



Gets the value as an Int64.



Gets the value as an Int.



Gets the value as a Bool.


It implements methods that report the status of A/B tests.


onReceived(result: DTDRemoteConfigReceiveResult)

It is triggered every time the SDK loads an A/B test configuration. If the remoteConfigWaiting has a default value (null), onReceived does not get called


It notifies the developer about coming changes in the A/B test configuration.

onChanged(result: DTDRemoteConfigChangeResult,

error: Error?)

It notifies the developer that the configuration has changed. Or about the reason why the configuration could not change.