React Native Academy · 课时

在 React Native 中设置 Supabase 客户端

创建 Supabase 项目，安装 @supabase/supabase-js，使用项目 URL 和匿名密钥初始化客户端，并将 AsyncStorage 配置为会话存储。

在 React Native 中设置 Supabase 客户端 是 CoddyKit 上的免费 React Native Academy 课时。这是第 1 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 React Native Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 React Native Academy 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

What Is Supabase?

Supabase is an open-source Firebase alternative that provides a hosted PostgreSQL database, authentication, real-time subscriptions, and file storage — all accessible through a simple JavaScript client. It is an excellent backend choice for React Native apps because it requires no server code for common operations.

Unlike Firebase, Supabase uses standard SQL and lets you query your data with full relational power. You create a project on supabase.com and get a project URL and an anon key that you use in your app.

Installing the Supabase JS Client

To use Supabase in a React Native project, install the official JavaScript client along with the AsyncStorage adapter that Supabase uses to persist auth sessions on mobile devices.

Run the following command in your project root. The @supabase/supabase-js package handles all API communication, while @react-native-async-storage/async-storage stores the session token between app launches.

npx expo install @supabase/supabase-js @react-native-async-storage/async-storage

Creating a Supabase Client Instance

You initialize the Supabase client once and export it for use throughout the app. Create a file called lib/supabase.ts and call createClient with your project URL and anon key.

The auth options tell the client to use AsyncStorage so the session persists after the app is closed, and detectSessionInUrl is set to false because React Native does not use browser URLs for OAuth callbacks.

import AsyncStorage from '@react-native-async-storage/async-storage';
import { createClient } from '@supabase/supabase-js';

const SUPABASE_URL = 'https://your-project.supabase.co';
const SUPABASE_ANON_KEY = 'your-anon-key';

export const supabase = createClient(SUPABASE_URL, SUPABASE_ANON_KEY, {
  auth: {
    storage: AsyncStorage,
    autoRefreshToken: true,
    persistSession: true,
    detectSessionInUrl: false,
  },
});

Where to Store Your Supabase Keys

Your Supabase URL and anon key are not secret — the anon key is meant to be used in client-side code and is protected by Row Level Security (RLS) policies in your database. However, your service_role key is secret and must never be embedded in a mobile app.

A best practice is to store the public keys in environment variables using a .env file and access them via process.env.EXPO_PUBLIC_SUPABASE_URL. Expo automatically exposes variables prefixed with EXPO_PUBLIC_ to the JavaScript bundle.

# .env
EXPO_PUBLIC_SUPABASE_URL=https://your-project.supabase.co
EXPO_PUBLIC_SUPABASE_ANON_KEY=your-anon-key

# lib/supabase.ts
const SUPABASE_URL = process.env.EXPO_PUBLIC_SUPABASE_URL!;
const SUPABASE_ANON_KEY = process.env.EXPO_PUBLIC_SUPABASE_ANON_KEY!;

Understanding Row Level Security

Row Level Security (RLS) is the cornerstone of Supabase security. When RLS is enabled on a table, every query from the anon or authenticated key is filtered through policies you define in SQL. Without RLS, anyone with your anon key can read or modify all rows.

A typical policy allows users to read only their own rows: USING (auth.uid() = user_id). You enable RLS in the Supabase dashboard under the Authentication > Policies section, or with SQL: ALTER TABLE posts ENABLE ROW LEVEL SECURITY;

-- Enable RLS on a table
ALTER TABLE posts ENABLE ROW LEVEL SECURITY;

-- Allow users to read only their own posts
CREATE POLICY 'Users read own posts'
  ON posts FOR SELECT
  USING (auth.uid() = user_id);

-- Allow users to insert posts for themselves
CREATE POLICY 'Users insert own posts'
  ON posts FOR INSERT
  WITH CHECK (auth.uid() = user_id);

Verifying the Client Setup

After creating the client, you can verify it is configured correctly by performing a simple health check query. Calling supabase.from('your_table').select('count') will return an error if the URL or key is wrong, or a result if the connection is successful.

A common pattern is to test the connection in a useEffect during development and log any errors. Remember to remove debug logging before publishing to production.

import { useEffect } from 'react';
import { supabase } from '../lib/supabase';

export default function App() {
  useEffect(() => {
    async function testConnection() {
      const { data, error } = await supabase.from('profiles').select('count');
      if (error) {
        console.error('Supabase connection error:', error.message);
      } else {
        console.log('Connected to Supabase:', data);
      }
    }
    testConnection();
  }, []);

  return null;
}

Auth Session Persistence with AsyncStorage

By setting storage: AsyncStorage in the Supabase client options, the auth session (JWT token and refresh token) is automatically saved to device storage. When the user reopens the app, the client reads this stored session and restores the authenticated state without requiring them to log in again.

You can listen to auth state changes with supabase.auth.onAuthStateChange, which fires whenever the session is created, refreshed, or destroyed. This is useful for driving your navigation stack.

import { useEffect, useState } from 'react';
import { Session } from '@supabase/supabase-js';
import { supabase } from '../lib/supabase';

export function useSession() {
  const [session, setSession] = useState<Session | null>(null);

  useEffect(() => {
    supabase.auth.getSession().then(({ data: { session } }) => {
      setSession(session);
    });

    const { data: { subscription } } = supabase.auth.onAuthStateChange(
      (_event, session) => setSession(session)
    );

    return () => subscription.unsubscribe();
  }, []);

  return session;
}

Supabase Project Dashboard Overview

The Supabase dashboard at app.supabase.com gives you a full view of your backend. Key sections include:

Table Editor — create and browse database tables visually
Auth — manage users, configure providers, and set policies
Storage — manage file buckets for images and documents
API — view auto-generated REST and real-time API documentation

The SQL Editor lets you run arbitrary SQL queries against your database, which is useful for creating tables, indexes, and RLS policies during development.

Creating a Profiles Table

A common pattern in Supabase apps is to create a profiles table that extends the built-in auth.users table with app-specific data like display names and avatars. You can use a database trigger to automatically create a profile row when a new user signs up.

The id column references auth.users, so each profile is linked to exactly one authenticated user. RLS policies ensure users can only read and update their own profile.

-- profiles table
CREATE TABLE profiles (
  id UUID PRIMARY KEY REFERENCES auth.users(id) ON DELETE CASCADE,
  username TEXT UNIQUE,
  avatar_url TEXT,
  created_at TIMESTAMPTZ DEFAULT now()
);

ALTER TABLE profiles ENABLE ROW LEVEL SECURITY;

CREATE POLICY 'Public profiles are viewable'
  ON profiles FOR SELECT USING (true);

CREATE POLICY 'Users update own profile'
  ON profiles FOR UPDATE USING (auth.uid() = id);

Auto-Refresh Token Behavior

Supabase JWTs expire after one hour by default. When you set autoRefreshToken: true in the client options, the client automatically calls the refresh endpoint before the token expires, keeping the user logged in without any intervention from your code.

If the refresh fails (for example, the user's internet is offline for an extended period), the client emits a TOKEN_REFRESHED event followed by a SIGNED_OUT event. You should handle SIGNED_OUT in your onAuthStateChange listener to redirect the user back to the login screen.

supabase.auth.onAuthStateChange((event, session) => {
  if (event === 'SIGNED_OUT') {
    // Navigate user to login screen
    navigation.reset({
      index: 0,
      routes: [{ name: 'Login' }],
    });
  }
  if (event === 'TOKEN_REFRESHED') {
    console.log('Token refreshed successfully');
  }
});

TypeScript Types from Supabase

Supabase can generate TypeScript types from your database schema using the Supabase CLI. Run npx supabase gen types typescript to produce a database.types.ts file. You then pass this as a generic to createClient for fully typed database queries.

Typed queries catch field-name typos at compile time and give you auto-complete in your editor — a significant productivity boost on larger projects.

import { Database } from './database.types';
import { createClient } from '@supabase/supabase-js';

export const supabase = createClient<Database>(
  process.env.EXPO_PUBLIC_SUPABASE_URL!,
  process.env.EXPO_PUBLIC_SUPABASE_ANON_KEY!
);

// Now queries are fully typed:
// supabase.from('profiles').select('id, username')
// TypeScript knows the shape of each row

Quick Check

Test your understanding of React Native Mobile Development concepts from this lesson.

Lesson Recap

In this lesson you learned: how to install and initialize the Supabase JS client, the role of AsyncStorage in persisting auth sessions, and why Row Level Security is essential when using the anon key in mobile apps. Next up we explore authentication flows with Supabase including email/password and OAuth providers.

常见问题解答

「在 React Native 中设置 Supabase 客户端」课时是免费的吗？

是的 — 「在 React Native 中设置 Supabase 客户端」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 React Native Academy 课程的其余内容，请升级到 CoddyKit PRO。 React Native Academy 课程共包含 4 节课。

「在 React Native 中设置 Supabase 客户端」这节课中我会学到什么？

创建 Supabase 项目，安装 @supabase/supabase-js，使用项目 URL 和匿名密钥初始化客户端，并将 AsyncStorage 配置为会话存储。你通过在浏览器中直接运行的动手代码来练习 React Native Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 React Native Academy 需要有经验吗？

无需任何先前经验。CoddyKit 上的 React Native Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 1 节课，共 4 节。

「在 React Native 中设置 Supabase 客户端」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 React Native Academy 课中编写并运行代码吗？

能。每节 React Native Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

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