---
title: Example usage of the Flutter SDK
slug: feature-experimentation/docs/example-usage-flutter
docTags: 
createdAt: 2026-08-05T20:39:56.000Z
---

After the Flutter SDK is installed, you can use the client to evaluate flag rules like A/B tests and flag deliveries.

This example walks through the following three key steps:

1. Evaluate a flag with the key `product_sort` using the `decide` method. This also sends a decision event to Optimizely to record that the user was exposed to the experiment.
2. Run code based on the flag result. The SDK evaluates your flag rules and determines which variation the user is in. You can either
   - Check the flag's enabled state and read a configuration variable (`sort_method`) to determine which experience the user gets.
   - Check the flag variation directly and run the corresponding control or treatment code.
3. Track a conversion event called `purchased` to measure the experiment's impact. The `trackEvent` method ties the purchase back to the A/B test and sends it to Optimizely so it displays on your [Experiment Results page](docId:_K6n7h_MZ8b0xn6yWPrrq).

```dart
// Initializing OptimizelyClient
var flutterSDK = OptimizelyFlutterSdk("<Your_SDK_Key>");
var response = await flutterSDK.initializeClient();
// flag decision
var user = await flutterSDK.createUserContext(userId: "user123");

var attributes = <String, dynamic>{};
attributes["logged_in"] = true;
user!.setAttributes(attributes);

var decideResponse = await user.decide("product_sort");

// did the decision fail with a critical error?
if (!decideResponse.success) {
 var reason = decideResponse.reason;
 print("decision error: $reason");
}
var decision = decideResponse.decision;
var variationKey = decision!.variationKey;

// execute code based on flag enabled state
var enabled = decision.enabled;
var variables = decision.variables;
if (enabled) {
 String vs;
 try {
   vs = variables["sort_method"] as String;
 } catch  (ex) {
   print(ex);
 }
}

// or execute code based on flag variation:
if (variationKey == "control") {
// Execute code for control variation
} else if (variationKey == "treatment") {
// Execute code for treatment variation
}

// Track an event
user.trackEvent("purchased");
```