The experiments module assigns users to variants using a deterministic hash. No server call is needed — assignment is instant, works offline, and the same user always gets the same variant.
Get Variant
final variant = AppDNA.experiments.getVariant("paywall-test");
if (variant == "variant_a") {
showNewPaywall();
} else {
showStandardPaywall(); // Always handle the default case
}
null if the experiment is not found, not running, or the user is not in the target audience.
Always handle the null / default case. Experiments can be archived or stopped at any time from the Console.
Module Access
final experiments = AppDNA.experiments;
Module Methods
| Method | Signature | Description |
|---|
getVariant | String? getVariant(String experimentId, {bool trackExposure = true}) | Get the assigned variant |
trackExposure | void trackExposure(String experimentId) | Manually track an exposure event |
set delegate | set delegate(ExperimentDelegate?) | Set a delegate for assignment callbacks |
Exposure Tracking
Automatic (Default)
The SDK tracks an experiment_exposure event once per session the first time getVariant() is called for a given experiment.
Manual
Disable automatic tracking and track when the UI is actually visible:
final variant = AppDNA.experiments.getVariant("paywall-test", trackExposure: false);
// Later, when the paywall is actually displayed
void onPaywallVisible() {
AppDNA.experiments.trackExposure("paywall-test");
}
ExperimentDelegate
class MyExperimentHandler extends ExperimentDelegate {
@override
void onAssignmentChanged(String experimentId, String? newVariant) {
print("Experiment $experimentId now: ${newVariant ?? 'none'}");
}
}
AppDNA.experiments.delegate = MyExperimentHandler();
Assignment changes are rare. They occur only when the experiment definition changes on the server, not on every session start.
Experiment Lifecycle
| Status | getVariant() returns |
|---|
| Draft | null — not visible to SDKs |
| Running | Assigned variant string |
| Completed | Winning variant for all users |
| Archived | null — removed from config |
Full Example
import 'package:appdna_sdk/appdna_sdk.dart';
class PaywallExperiment extends ExperimentDelegate {
PaywallExperiment() {
AppDNA.experiments.delegate = this;
}
void showPaywall() {
final variant = AppDNA.experiments.getVariant("paywall_redesign");
final paywallId = variant == "new_design" ? "paywall_v2" : "paywall_v1";
AppDNA.paywall.present(
paywallId,
context: PaywallContext(
placement: "settings",
experiment: "paywall_redesign",
variant: variant ?? "control",
),
);
}
@override
void onAssignmentChanged(String experimentId, String? newVariant) {
// Assignment changed mid-session (rare)
}
}
Experiments are created in the Console under Experiments. The SDK uses MurmurHash3 for deterministic assignment — the same user always gets the same variant across sessions, platforms, and offline.
