File API - Swift SDK Documentation

Overview

The File API provides endpoints for downloading and accessing files stored in collection records. It supports thumbnail generation for images, protected file access with tokens, and force download options.

Key Features:

Download files from collection records
Generate thumbnails for images (crop, fit, resize)
Protected file access with short-lived tokens
Force download option for any file type
Automatic content-type detection
Support for Range requests and caching

Backend Endpoints:

GET /api/files/{collection}/{recordId}/{filename} - Download/fetch file
POST /api/files/token - Generate protected file token

Download / Fetch File

Downloads a single file resource from a record.

Basic Usage

import BosBase

let client = try BosBaseClient(baseURLString: "http://127.0.0.1:8090")

// Get a record with a file field
let record: JSONRecord = try await client
    .collection("posts")
    .getOne("RECORD_ID")

// Get the file URL
if let filename = record["image"]?.value as? String,
   let fileURL = client.files.getURL(record: record, filename: filename) {
    // Use the URL
    print("File URL: \(fileURL)")
}

File URL Structure

The file URL follows this pattern:

/api/files/{collectionIdOrName}/{recordId}/{filename}

Example:

http://127.0.0.1:8090/api/files/posts/abc123/photo_xyz789.jpg

Thumbnails

Generate thumbnails for image files on-the-fly.

Thumbnail Formats

The following thumbnail formats are supported:

Format	Example	Description
`WxH`	`100x300`	Crop to WxH viewbox (from center)
`WxHt`	`100x300t`	Crop to WxH viewbox (from top)
`WxHb`	`100x300b`	Crop to WxH viewbox (from bottom)
`WxHf`	`100x300f`	Fit inside WxH viewbox (without cropping)
`0xH`	`0x300`	Resize to H height preserving aspect ratio
`Wx0`	`100x0`	Resize to W width preserving aspect ratio

Using Thumbnails

// Get thumbnail URL
if let filename = record["image"]?.value as? String {
    let thumbURL = client.files.getURL(
        record: record,
        filename: filename,
        options: FileOptions(thumb: "100x100")
    )
    
    // Different thumbnail sizes
    let smallThumb = client.files.getURL(
        record: record,
        filename: filename,
        options: FileOptions(thumb: "50x50")
    )
    
    let mediumThumb = client.files.getURL(
        record: record,
        filename: filename,
        options: FileOptions(thumb: "200x200")
    )
    
    let largeThumb = client.files.getURL(
        record: record,
        filename: filename,
        options: FileOptions(thumb: "500x500")
    )
    
    // Fit thumbnail (no cropping)
    let fitThumb = client.files.getURL(
        record: record,
        filename: filename,
        options: FileOptions(thumb: "200x200f")
    )
    
    // Resize to specific width
    let widthThumb = client.files.getURL(
        record: record,
        filename: filename,
        options: FileOptions(thumb: "300x0")
    )
    
    // Resize to specific height
    let heightThumb = client.files.getURL(
        record: record,
        filename: filename,
        options: FileOptions(thumb: "0x200")
    )
}

Thumbnail Behavior

Image Files Only: Thumbnails are only generated for image files (PNG, JPG, JPEG, GIF, WEBP)
Non-Image Files: For non-image files, the thumb parameter is ignored and the original file is returned
Caching: Thumbnails are cached and reused if already generated
Fallback: If thumbnail generation fails, the original file is returned
Field Configuration: Thumb sizes must be defined in the file field’s thumbs option or use default 100x100

Protected Files

Protected files require a special token for access, even if you’re authenticated.

Getting a File Token

// Must be authenticated first
try await client
    .collection("users")
    .authWithPassword(identity: "user@example.com", password: "password")

// Get file token
let token = try await client.files.getToken()

print("Token: \(token)") // Short-lived JWT token

Using Protected File Token

// Get protected file URL with token
if let filename = record["document"]?.value as? String {
    let protectedFileURL = client.files.getURL(
        record: record,
        filename: filename,
        options: FileOptions(token: token)
    )
    
    // Access the file
    if let url = protectedFileURL {
        let data = try Data(contentsOf: url)
        // Use the file data
    }
}

Protected File Example

func displayProtectedImage(recordId: String) async throws {
    // Authenticate
    try await client
        .collection("users")
        .authWithPassword(identity: "user@example.com", password: "password")
    
    // Get record
    let record: JSONRecord = try await client
        .collection("documents")
        .getOne(recordId)
    
    // Get file token
    let token = try await client.files.getToken()
    
    // Get protected file URL
    if let filename = record["thumbnail"]?.value as? String {
        let imageURL = client.files.getURL(
            record: record,
            filename: filename,
            options: FileOptions(
                token: token,
                thumb: "300x300"
            )
        )
        
        // Display image (in UI framework)
        print("Image URL: \(imageURL?.absoluteString ?? "")")
    }
}

Token Lifetime

File tokens are short-lived (typically expires after a few minutes)
Tokens are associated with the authenticated user/superuser
Generate a new token if the previous one expires

Force Download

Force files to download instead of being displayed in the browser.

// Force download
if let filename = record["document"]?.value as? String {
    let downloadURL = client.files.getURL(
        record: record,
        filename: filename,
        options: FileOptions(download: true)
    )
    
    // Use the download URL
    if let url = downloadURL {
        // Trigger download (platform-specific)
        #if canImport(UIKit)
        // iOS: Use URLSession or WKWebView
        #elseif canImport(AppKit)
        // macOS: Use NSWorkspace
        NSWorkspace.shared.open(url)
        #endif
    }
}

Complete Examples

Example 1: Image Gallery

func displayImageGallery(recordId: String) async throws {
    let record: JSONRecord = try await client
        .collection("posts")
        .getOne(recordId)
    
    let images: [String] = {
        if let imagesArray = record["images"]?.value as? [String] {
            return imagesArray
        } else if let singleImage = record["image"]?.value as? String {
            return [singleImage]
        }
        return []
    }()
    
    for filename in images {
        // Thumbnail for gallery
        if let thumbURL = client.files.getURL(
            record: record,
            filename: filename,
            options: FileOptions(thumb: "200x200")
        ) {
            print("Thumbnail: \(thumbURL)")
        }
        
        // Full image URL
        if let fullURL = client.files.getURL(record: record, filename: filename) {
            print("Full image: \(fullURL)")
        }
    }
}

Example 2: File Download Handler

func downloadFile(recordId: String, filename: String) async throws {
    let record: JSONRecord = try await client
        .collection("documents")
        .getOne(recordId)
    
    // Get download URL
    if let downloadURL = client.files.getURL(
        record: record,
        filename: filename,
        options: FileOptions(download: true)
    ) {
        // Download the file
        let data = try Data(contentsOf: downloadURL)
        
        // Save to file system
        let documentsPath = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
        let fileURL = documentsPath.appendingPathComponent(filename)
        try data.write(to: fileURL)
        
        print("File saved to: \(fileURL.path)")
    }
}

Example 3: Protected File Viewer

func viewProtectedFile(recordId: String) async throws {
    // Authenticate
    if !client.authStore.isValid() {
        try await client
            .collection("users")
            .authWithPassword(identity: "user@example.com", password: "password")
    }
    
    // Get record
    let record: JSONRecord = try await client
        .collection("private_docs")
        .getOne(recordId)
    
    // Get token
    let token: String
    do {
        token = try await client.files.getToken()
    } catch {
        print("Failed to get file token: \(error)")
        return
    }
    
    // Get file URL
    if let filename = record["file"]?.value as? String {
        let fileURL = client.files.getURL(
            record: record,
            filename: filename,
            options: FileOptions(token: token)
        )
        
        // Display based on file type
        let ext = (filename as NSString).pathExtension.lowercased()
        
        if ["jpg", "jpeg", "png", "gif", "webp"].contains(ext) {
            // Display image
            print("Image URL: \(fileURL?.absoluteString ?? "")")
        } else if ["pdf"].contains(ext) {
            // Display PDF
            print("PDF URL: \(fileURL?.absoluteString ?? "")")
        } else {
            // Download other files
            try await downloadFile(recordId: recordId, filename: filename)
        }
    }
}

Error Handling

do {
    if let filename = record["image"]?.value as? String,
       let fileURL = client.files.getURL(record: record, filename: filename) {
        // Verify URL is valid
        let data = try Data(contentsOf: fileURL)
        print("File loaded successfully")
    } else {
        print("Invalid file URL")
    }
} catch {
    print("File access error: \(error)")
}

Protected File Token Error Handling

func getProtectedFileURL(record: JSONRecord, filename: String) async throws -> URL? {
    do {
        // Get token
        let token = try await client.files.getToken()
        
        // Get file URL
        return client.files.getURL(
            record: record,
            filename: filename,
            options: FileOptions(token: token)
        )
    } catch let error as ClientResponseError {
        if error.status == 401 {
            print("Not authenticated")
            // Redirect to login
        } else if error.status == 403 {
            print("No permission to access file")
        } else {
            print("Failed to get file token: \(error)")
        }
        return nil
    } catch {
        print("Unexpected error: \(error)")
        return nil
    }
}

Best Practices

Use Thumbnails for Lists: Use thumbnails when displaying images in lists/grids to reduce bandwidth
Lazy Loading: Load images on demand to improve performance
Cache Tokens: Store file tokens and reuse them until they expire
Error Handling: Always handle file loading errors gracefully
Content-Type: Let the server handle content-type detection automatically
Range Requests: The API supports Range requests for efficient video/audio streaming
Caching: Files are cached with a 30-day cache-control header
Security: Always use tokens for protected files, never expose them in client-side code

Thumbnail Size Guidelines

Use Case	Recommended Size
Profile picture	`100x100` or `150x150`
List thumbnails	`200x200` or `300x300`
Card images	`400x400` or `500x500`
Gallery previews	`300x300f` (fit) or `400x400f`
Hero images	Use original or `800x800f`
Avatar	`50x50` or `75x75`

Limitations

Thumbnails: Only work for image files (PNG, JPG, JPEG, GIF, WEBP)
Protected Files: Require authentication to get tokens
Token Expiry: File tokens expire after a short period (typically minutes)
File Size: Large files may take time to generate thumbnails on first request
Thumb Sizes: Must match sizes defined in field configuration or use default 100x100

Files Upload and Handling - Uploading and managing files
API Records - Working with records
Collections - Collection configuration