Supabase Backend as a Service · 课时

上传并获取媒体文件

练习上传图像、视频和其他媒体文件，然后获取它们以在应用中显示。

上传并获取媒体文件 是 CoddyKit 上的免费 Supabase Backend as a Service 课时。这是第 3 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 Supabase Backend as a Service 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Supabase Backend as a Service 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。

Media for Dynamic Apps

User avatars, product images, videos – media makes applications rich and engaging. Learning to manage files effectively is crucial for modern app development.

In this lesson, we'll focus on using the Supabase Storage client to upload various media types and retrieve them for display.

The Supabase Storage Client

The supabase.storage client is your gateway to interacting with file storage. It allows you to perform operations like uploading, downloading, and managing files within your Supabase buckets.

You'll typically initialize your Supabase client once in your application.

Preparing Files for Upload

Before you can upload a file, you need its data. In web applications, this often comes from an HTML <input type="file"> element, giving you a File or Blob object.

For our examples, we'll simulate a Blob object to represent file data, making the code runnable.

Uploading Your First File

Use the upload() method to send a file to a specific bucket path. You'll need to specify the bucket name, the desired file path (including the filename), and the file's data.

Try running this example to see a simulated file upload:

// Assume 'createClient' is imported from '@supabase/supabase-js'
// Assume 'SUPABASE_URL' and 'SUPABASE_ANON_KEY' are configured

const createClient = (url, key) => ({
  storage: {
    from: (bucketName) => ({
      upload: async (filePath, fileData, options) => {
        console.log(`[MOCK] Uploading to bucket '${bucketName}', path '${filePath}'`);
        console.log(`[MOCK] File data type: ${fileData.type}, size: ${fileData.size}`);
        console.log(`[MOCK] Options: ${JSON.stringify(options)}`);
        return { data: { path: filePath, id: 'mock-id' }, error: null };
      }
    })
  }
});

const SUPABASE_URL = 'https://your-project.supabase.co'; // Replace with your URL
const SUPABASE_ANON_KEY = 'YOUR_ANON_KEY'; // Replace with your Anon Key
const supabase = createClient(SUPABASE_URL, SUPABASE_ANON_KEY);

async function uploadExample() {
  const fileData = new Blob(['Hello CoddyKit!'], { type: 'text/plain' });
  const fileName = 'lesson-note.txt';
  const filePath = `public/${fileName}`; // Store in a 'public' folder

  try {
    const { data, error } = await supabase
      .storage
      .from('my-bucket') // Use your actual bucket name
      .upload(filePath, fileData, {
        cacheControl: '3600', // Cache for 1 hour
        upsert: false // Do not overwrite if file exists
      });

    if (error) {
      throw error;
    }
    console.log('Upload successful:', data);
  } catch (error) {
    console.error('Error uploading file:', error.message);
  }
}

uploadExample();

Understanding Upload Options

The upload() method accepts an options object to fine-tune the upload process:

cacheControl: Sets the Cache-Control header, telling browsers how long to cache the file.
upsert: A boolean. If true, an existing file at the specified path will be overwritten. If false (default), it will error if the file exists.
contentType: The MIME type of the file (e.g., 'image/jpeg'). Often inferred, but good to set explicitly for accuracy.

Retrieving Public URLs

For files stored in buckets with public access (configured via Storage Policies), you can get a direct, publicly accessible URL. This URL can be used in <img> tags, <video> tags, or as direct download links.

The getPublicUrl() method will give you this link.

// Assume 'createClient' is imported and configured
const createClient = (url, key) => ({
  storage: {
    from: (bucketName) => ({
      getPublicUrl: (filePath) => {
        console.log(`[MOCK] Getting public URL for bucket '${bucketName}', path '${filePath}'`);
        return { data: { publicUrl: `https://mock.supabase.co/storage/v1/object/public/${bucketName}/${filePath}` } };
      }
    })
  }
});

const SUPABASE_URL = 'https://your-project.supabase.co';
const SUPABASE_ANON_KEY = 'YOUR_ANON_KEY';
const supabase = createClient(SUPABASE_URL, SUPABASE_ANON_KEY);

function getPublicUrlExample() {
  const filePath = 'public/lesson-note.txt'; // Path of your uploaded file
  const { data } = supabase
    .storage
    .from('my-bucket') // Use your actual bucket name
    .getPublicUrl(filePath);

  console.log('Public URL:', data.publicUrl);
}

getPublicUrlExample();

Displaying Media in Your App

Once you have the public URL from getPublicUrl(), displaying media in your application is straightforward. You simply use the URL in the appropriate HTML element's src attribute.

Images: <img src="YOUR_PUBLIC_URL" alt="description">
Videos: <video src="YOUR_PUBLIC_URL" controls></video>
Audio: <audio src="YOUR_PUBLIC_URL" controls></audio>

Securely Accessing Private Media

Not all files should be publicly accessible. For private files (e.g., user documents, sensitive media) protected by RLS policies, you can't use a simple public URL.

Supabase provides signed URLs for secure, temporary access to these private files. These URLs include a temporary token that expires after a set duration.

Generating Signed URLs

The createSignedUrl() method generates a temporary URL for a private file. You specify the file path and how long (in seconds) the URL should be valid.

This is ideal for scenarios where you want to grant authenticated users temporary access to private content without making it globally public.

// Assume 'createClient' is imported and configured
const createClient = (url, key) => ({
  storage: {
    from: (bucketName) => ({
      createSignedUrl: async (filePath, expiresIn) => {
        console.log(`[MOCK] Creating signed URL for bucket '${bucketName}', path '${filePath}', expires in ${expiresIn}s`);
        return { data: { signedUrl: `https://mock.supabase.co/storage/v1/object/sign/${bucketName}/${filePath}?token=mock-token&expires=${expiresIn}` }, error: null };
      }
    })
  }
});

const SUPABASE_URL = 'https://your-project.supabase.co';
const SUPABASE_ANON_KEY = 'YOUR_ANON_KEY';
const supabase = createClient(SUPABASE_URL, SUPABASE_ANON_KEY);

async function getSignedUrlExample() {
  const privateFilePath = 'private/user-report.pdf'; // Path to a private file
  const expiresInSeconds = 60; // URL valid for 60 seconds

  try {
    const { data, error } = await supabase
      .storage
      .from('my-private-bucket') // Use your actual private bucket name
      .createSignedUrl(privateFilePath, expiresInSeconds);

    if (error) {
      throw error;
    }
    console.log('Signed URL:', data.signedUrl);
    console.log(`This URL will expire in ${expiresInSeconds} seconds.`);
  } catch (error) {
    console.error('Error creating signed URL:', error.message);
  }
}

getSignedUrlExample();

Upload & Retrieve Check

Let's test your understanding of uploading and retrieving media with Supabase Storage.

Media Management Mastered

You've successfully learned how to:

Upload files to Supabase Storage buckets using upload().
Retrieve public URLs for immediate display with getPublicUrl().
Generate secure, time-limited signed URLs for private content using createSignedUrl().

These skills are fundamental for building rich, dynamic applications that handle user-generated content or managed media assets securely and efficiently.

常见问题解答

「上传并获取媒体文件」课时是免费的吗？

是的 — 「上传并获取媒体文件」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 Supabase Backend as a Service 课程的其余内容，请升级到 CoddyKit PRO。 Supabase Backend as a Service 课程共包含 4 节课。

「上传并获取媒体文件」这节课中我会学到什么？

练习上传图像、视频和其他媒体文件，然后获取它们以在应用中显示。你通过在浏览器中直接运行的动手代码来练习 Supabase Backend as a Service，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 Supabase Backend as a Service 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Supabase Backend as a Service 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 3 节课，共 4 节。

「上传并获取媒体文件」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 Supabase Backend as a Service 课中编写并运行代码吗？

能。每节 Supabase Backend as a Service 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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