native-data-fetching/.skillshare-meta.json

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+{
+  "source": "github.com/expo/skills/tree/main/plugins/expo-app-design/skills/native-data-fetching",
+  "type": "github-subdir",
+  "installed_at": "2026-01-30T02:26:56.038194184Z",
+  "repo_url": "https://github.com/expo/skills.git",
+  "subdir": "plugins/expo-app-design/skills/native-data-fetching",
+  "version": "b631a60"
+}

native-data-fetching/SKILL.md

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+---
+name: native-data-fetching
+description: Use when implementing or debugging ANY network request, API call, or data fetching. Covers fetch API, axios, React Query, SWR, error handling, caching strategies, offline support.
+version: 1.0.0
+license: MIT
+---
+
+# Expo Networking
+
+**You MUST use this skill for ANY networking work including API requests, data fetching, caching, or network debugging.**
+
+## When to Use
+
+Use this router when:
+
+- Implementing API requests
+- Setting up data fetching (React Query, SWR)
+- Debugging network failures
+- Implementing caching strategies
+- Handling offline scenarios
+- Authentication/token management
+- Configuring API URLs and environment variables
+
+## Preferences
+
+- Avoid axios, prefer expo/fetch
+
+## Common Issues & Solutions
+
+### 1. Basic Fetch Usage
+
+**Simple GET request**:
+
+```tsx
+const fetchUser = async (userId: string) => {
+  const response = await fetch(`https://api.example.com/users/${userId}`);
+
+  if (!response.ok) {
+    throw new Error(`HTTP error! status: ${response.status}`);
+  }
+
+  return response.json();
+};
+```
+
+**POST request with body**:
+
+```tsx
+const createUser = async (userData: UserData) => {
+  const response = await fetch("https://api.example.com/users", {
+    method: "POST",
+    headers: {
+      "Content-Type": "application/json",
+      Authorization: `Bearer ${token}`,
+    },
+    body: JSON.stringify(userData),
+  });
+
+  if (!response.ok) {
+    const error = await response.json();
+    throw new Error(error.message);
+  }
+
+  return response.json();
+};
+```
+
+---
+
+### 2. React Query (TanStack Query)
+
+**Setup**:
+
+```tsx
+// app/_layout.tsx
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+
+const queryClient = new QueryClient({
+  defaultOptions: {
+    queries: {
+      staleTime: 1000 * 60 * 5, // 5 minutes
+      retry: 2,
+    },
+  },
+});
+
+export default function RootLayout() {
+  return (
+    <QueryClientProvider client={queryClient}>
+      <Stack />
+    </QueryClientProvider>
+  );
+}
+```
+
+**Fetching data**:
+
+```tsx
+import { useQuery } from "@tanstack/react-query";
+
+function UserProfile({ userId }: { userId: string }) {
+  const { data, isLoading, error, refetch } = useQuery({
+    queryKey: ["user", userId],
+    queryFn: () => fetchUser(userId),
+  });
+
+  if (isLoading) return <Loading />;
+  if (error) return <Error message={error.message} />;
+
+  return <Profile user={data} />;
+}
+```
+
+**Mutations**:
+
+```tsx
+import { useMutation, useQueryClient } from "@tanstack/react-query";
+
+function CreateUserForm() {
+  const queryClient = useQueryClient();
+
+  const mutation = useMutation({
+    mutationFn: createUser,
+    onSuccess: () => {
+      // Invalidate and refetch
+      queryClient.invalidateQueries({ queryKey: ["users"] });
+    },
+  });
+
+  const handleSubmit = (data: UserData) => {
+    mutation.mutate(data);
+  };
+
+  return <Form onSubmit={handleSubmit} isLoading={mutation.isPending} />;
+}
+```
+
+---
+
+### 3. Error Handling
+
+**Comprehensive error handling**:
+
+```tsx
+class ApiError extends Error {
+  constructor(message: string, public status: number, public code?: string) {
+    super(message);
+    this.name = "ApiError";
+  }
+}
+
+const fetchWithErrorHandling = async (url: string, options?: RequestInit) => {
+  try {
+    const response = await fetch(url, options);
+
+    if (!response.ok) {
+      const error = await response.json().catch(() => ({}));
+      throw new ApiError(
+        error.message || "Request failed",
+        response.status,
+        error.code
+      );
+    }
+
+    return response.json();
+  } catch (error) {
+    if (error instanceof ApiError) {
+      throw error;
+    }
+    // Network error (no internet, timeout, etc.)
+    throw new ApiError("Network error", 0, "NETWORK_ERROR");
+  }
+};
+```
+
+**Retry logic**:
+
+```tsx
+const fetchWithRetry = async (
+  url: string,
+  options?: RequestInit,
+  retries = 3
+) => {
+  for (let i = 0; i < retries; i++) {
+    try {
+      return await fetchWithErrorHandling(url, options);
+    } catch (error) {
+      if (i === retries - 1) throw error;
+      // Exponential backoff
+      await new Promise((r) => setTimeout(r, Math.pow(2, i) * 1000));
+    }
+  }
+};
+```
+
+---
+
+### 4. Authentication
+
+**Token management**:
+
+```tsx
+import * as SecureStore from "expo-secure-store";
+
+const TOKEN_KEY = "auth_token";
+
+export const auth = {
+  getToken: () => SecureStore.getItemAsync(TOKEN_KEY),
+  setToken: (token: string) => SecureStore.setItemAsync(TOKEN_KEY, token),
+  removeToken: () => SecureStore.deleteItemAsync(TOKEN_KEY),
+};
+
+// Authenticated fetch wrapper
+const authFetch = async (url: string, options: RequestInit = {}) => {
+  const token = await auth.getToken();
+
+  return fetch(url, {
+    ...options,
+    headers: {
+      ...options.headers,
+      Authorization: token ? `Bearer ${token}` : "",
+    },
+  });
+};
+```
+
+**Token refresh**:
+
+```tsx
+let isRefreshing = false;
+let refreshPromise: Promise<string> | null = null;
+
+const getValidToken = async (): Promise<string> => {
+  const token = await auth.getToken();
+
+  if (!token || isTokenExpired(token)) {
+    if (!isRefreshing) {
+      isRefreshing = true;
+      refreshPromise = refreshToken().finally(() => {
+        isRefreshing = false;
+        refreshPromise = null;
+      });
+    }
+    return refreshPromise!;
+  }
+
+  return token;
+};
+```
+
+---
+
+### 5. Offline Support
+
+**Check network status**:
+
+```tsx
+import NetInfo from "@react-native-community/netinfo";
+
+// Hook for network status
+function useNetworkStatus() {
+  const [isOnline, setIsOnline] = useState(true);
+
+  useEffect(() => {
+    return NetInfo.addEventListener((state) => {
+      setIsOnline(state.isConnected ?? true);
+    });
+  }, []);
+
+  return isOnline;
+}
+```
+
+**Offline-first with React Query**:
+
+```tsx
+import { onlineManager } from "@tanstack/react-query";
+import NetInfo from "@react-native-community/netinfo";
+
+// Sync React Query with network status
+onlineManager.setEventListener((setOnline) => {
+  return NetInfo.addEventListener((state) => {
+    setOnline(state.isConnected ?? true);
+  });
+});
+
+// Queries will pause when offline and resume when online
+```
+
+---
+
+### 6. Environment Variables
+
+**Using environment variables for API configuration**:
+
+Expo supports environment variables with the `EXPO_PUBLIC_` prefix. These are inlined at build time and available in your JavaScript code.
+
+```tsx
+// .env
+EXPO_PUBLIC_API_URL=https://api.example.com
+EXPO_PUBLIC_API_VERSION=v1
+
+// Usage in code
+const API_URL = process.env.EXPO_PUBLIC_API_URL;
+
+const fetchUsers = async () => {
+  const response = await fetch(`${API_URL}/users`);
+  return response.json();
+};
+```
+
+**Environment-specific configuration**:
+
+```tsx
+// .env.development
+EXPO_PUBLIC_API_URL=http://localhost:3000
+
+// .env.production
+EXPO_PUBLIC_API_URL=https://api.production.com
+```
+
+**Creating an API client with environment config**:
+
+```tsx
+// api/client.ts
+const BASE_URL = process.env.EXPO_PUBLIC_API_URL;
+
+if (!BASE_URL) {
+  throw new Error("EXPO_PUBLIC_API_URL is not defined");
+}
+
+export const apiClient = {
+  get: async <T,>(path: string): Promise<T> => {
+    const response = await fetch(`${BASE_URL}${path}`);
+    if (!response.ok) throw new Error(`HTTP ${response.status}`);
+    return response.json();
+  },
+
+  post: async <T,>(path: string, body: unknown): Promise<T> => {
+    const response = await fetch(`${BASE_URL}${path}`, {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify(body),
+    });
+    if (!response.ok) throw new Error(`HTTP ${response.status}`);
+    return response.json();
+  },
+};
+```
+
+**Important notes**:
+
+- Only variables prefixed with `EXPO_PUBLIC_` are exposed to the client bundle
+- Never put secrets (API keys with write access, database passwords) in `EXPO_PUBLIC_` variables—they're visible in the built app
+- Environment variables are inlined at **build time**, not runtime
+- Restart the dev server after changing `.env` files
+- For server-side secrets in API routes, use variables without the `EXPO_PUBLIC_` prefix
+
+**TypeScript support**:
+
+```tsx
+// types/env.d.ts
+declare global {
+  namespace NodeJS {
+    interface ProcessEnv {
+      EXPO_PUBLIC_API_URL: string;
+      EXPO_PUBLIC_API_VERSION?: string;
+    }
+  }
+}
+
+export {};
+```
+
+---
+
+### 7. Request Cancellation
+
+**Cancel on unmount**:
+
+```tsx
+useEffect(() => {
+  const controller = new AbortController();
+
+  fetch(url, { signal: controller.signal })
+    .then((response) => response.json())
+    .then(setData)
+    .catch((error) => {
+      if (error.name !== "AbortError") {
+        setError(error);
+      }
+    });
+
+  return () => controller.abort();
+}, [url]);
+```
+
+**With React Query** (automatic):
+
+```tsx
+// React Query automatically cancels requests when queries are invalidated
+// or components unmount
+```
+
+---
+
+## Decision Tree
+
+```
+User asks about networking
+  |-- Basic fetch?
+  |   \-- Use fetch API with error handling
+  |
+  |-- Need caching/state management?
+  |   |-- Complex app -> React Query (TanStack Query)
+  |   \-- Simpler needs -> SWR or custom hooks
+  |
+  |-- Authentication?
+  |   |-- Token storage -> expo-secure-store
+  |   \-- Token refresh -> Implement refresh flow
+  |
+  |-- Error handling?
+  |   |-- Network errors -> Check connectivity first
+  |   |-- HTTP errors -> Parse response, throw typed errors
+  |   \-- Retries -> Exponential backoff
+  |
+  |-- Offline support?
+  |   |-- Check status -> NetInfo
+  |   \-- Queue requests -> React Query persistence
+  |
+  |-- Environment/API config?
+  |   |-- Client-side URLs -> EXPO_PUBLIC_ prefix in .env
+  |   |-- Server secrets -> Non-prefixed env vars (API routes only)
+  |   \-- Multiple environments -> .env.development, .env.production
+  |
+  \-- Performance?
+      |-- Caching -> React Query with staleTime
+      |-- Deduplication -> React Query handles this
+      \-- Cancellation -> AbortController or React Query
+```
+
+## Common Mistakes
+
+**Wrong: No error handling**
+
+```tsx
+const data = await fetch(url).then((r) => r.json());
+```
+
+**Right: Check response status**
+
+```tsx
+const response = await fetch(url);
+if (!response.ok) throw new Error(`HTTP ${response.status}`);
+const data = await response.json();
+```
+
+**Wrong: Storing tokens in AsyncStorage**
+
+```tsx
+await AsyncStorage.setItem("token", token); // Not secure!
+```
+
+**Right: Use SecureStore for sensitive data**
+
+```tsx
+await SecureStore.setItemAsync("token", token);
+```
+
+## Example Invocations
+
+User: "How do I make API calls in React Native?"
+-> Use fetch, wrap with error handling
+
+User: "Should I use React Query or SWR?"
+-> React Query for complex apps, SWR for simpler needs
+
+User: "My app needs to work offline"
+-> Use NetInfo for status, React Query persistence for caching
+
+User: "How do I handle authentication tokens?"
+-> Store in expo-secure-store, implement refresh flow
+
+User: "API calls are slow"
+-> Check caching strategy, use React Query staleTime
+
+User: "How do I configure different API URLs for dev and prod?"
+-> Use EXPO*PUBLIC* env vars with .env.development and .env.production files
+
+User: "Where should I put my API key?"
+-> Client-safe keys: EXPO*PUBLIC* in .env. Secret keys: non-prefixed env vars in API routes only