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Statsig in Expo

Installation

To use Statsig in Expo, you will need to install the Statsig Expo specific bindings.

npx expo install @statsig/expo-bindings

Peer Dependencies

The @statsig/expo-bindings package has peer dependencies which may also need to be installed if they are not already in your project.

npx expo install expo-device expo-application @react-native-async-storage/async-storage

Expo + React Specific Setup

The setup for an Expo environment is very similar to a plain React environment. The only difference is that you need to use the Expo specific StatsigProviderExpo. This automatically switches out the storage layer used by the SDK, utilizing AsyncStorage instead of LocalStorage (which isn't available in RN environments).

import {
StatsigProviderExpo,
useFeatureGate,
} from '@statsig/expo-bindings';

function Content() {
const gate = useFeatureGate('a_gate');

return <Text>Reason: {gate.details.reason}</Text>; // Reason: Network or NetworkNotModified
}

function App() {
return (
<StatsigProviderExpo
sdkKey={YOUR_CLIENT_KEY}
user={{userID: 'a-user'}}
options={{ environment: { tier: 'development' } }} // (Optional)
loadingComponent={<Text>Loading...</Text>}>
<Content />
</StatsigProviderExpo>
);
}

The Basics

You can get an instance of the StatsigClient to check gates, experiments, dynamic configs, layers, and log events.

import { useStatsigClient } from "@statsig/react-native-expo-bindings";

const { client } = useStatsigClient();

See the methods you can call on the client below.

Checking a Feature Flag/Gate

You can evaluate a gate by getting the client with the useStatsigClient hook, and then calling checkGate

const { client } = useStatsigClient();
return (
<div>Gate is {client.checkGate('check_user') ? 'passing' : 'failing'}.</div>
);

Getting a DynamicConfig

You can get a DynamicConfig value by getting the client with the useStatsigClient hook, and then calling getConfig

const { client } = useStatsigClient();
const config = client.getConfig('app_properties');

return (
<div>{config.get('title', 'Default Title')}</div>
);

Logging an Event

You can get the client with the useStatsigClient hook, and then call logEvent

const { client } = useStatsigClient();
return <button onClick={() => client.logEvent("button_click")}>Click Me</button>

Getting an Experiment

You can access the experiment variant and parameters for the user by getting the client with the useStatsigClient hook, and then calling getExperiment.

const { client } = useStatsigClient();
const experiment = client.getExperiment('headline_test');

return (
<div>Headline Parameter: {experiment.get('headline', 'Default')}.</div>
);

Getting a Layer

You can access layers and layer parameters for the user by getting the client with the useStatsigClient hook, and then calling getLayer.

const { client } = useStatsigClient();
const layer = client.getLayer('homepage_layer');

return (
<div>Headline Parameter: {layer.get('hero_text', 'Welcome')}.</div>
);

Advanced

Expo Without React

In some scenarios, you may need to use the StatsigClient when you are not in the React component tree. Things like background tasks or handling notifications. For these, you can use the Expo specific StatsigClientExpo.

import { StatsigClientExpo } from '@statsig/expo-bindings';

const myClient = new StatsigClientExpo(
YOUR_CLIENT_KEY,
{ userID: "a-user" }
);

await myClient.initializeAsync();

if (myClient.checkGate("my_gate")) {
// do something cool
}

Synchronous Storage with MMKV

If you are utilizing MMKV in your project, and would prefer to use that instead of the default (AsyncStorage). You can provide you own StorageProvider via StatsigOptions.

Something like:

import { MMKV } from "react-native-mmkv";
import { StorageProvider } from "@statsig/client-core";
import { StatsigProviderExpo } from "@statsig/expo-bindings";

function App() {
const [storageProvider] = useState<StorageProvider>(() => {
const mmkv = new MMKV();

return {
isReady: () => true,
isReadyResolver: () => null,
getProviderName: () => "MMKV",
getAllKeys: () => mmkv.getAllKeys(),
getItem: (key: string) => mmkv.getString(key) ?? null,
setItem: (key: string, value: string) => mmkv.set(key, value),
removeItem: (key: string) => mmkv.delete(key),
};
});

return (
<StatsigProviderExpo
sdkKey={YOUR_CLIENT_KEY}
user={{ userID: "a-user" }}
options={{
storageProvider, // <- Passed into StatsigOptions
}}
>
<Text>...</Text>
</StatsigProviderExpo>
);
}