dat-conventions

Instruction file imported from facebook/meta-wearables-dat-ios (.cursor/rules/dat-conventions.mdc). Copyright stays with the author.

DAT SDK Conventions (iOS)

Architecture

The public SDK is organized into these modules:

• MWDATCore: Device discovery, registration, permissions, device selectors, DeviceSession
• MWDATCamera: Camera, Stream, VideoFrame, photo capture
• MWDATDisplay: Display capability, display UI components, icons, images, buttons, video
• MWDATMockDevice: MockDeviceKit for testing without hardware
• MWDATMockDeviceTestClient: MockDeviceTestClient for driving MockDeviceKit over HTTP from a UI-test process

Swift Patterns

• Use async/await for all SDK operations — the SDK is fully async
• Use AsyncSequence / publisher .listen {} for observing streams
• Annotate UI-updating code with @MainActor
• Never block the main thread with frame processing
• Handle errors with do/catch — the SDK throws typed errors

Naming Conventions

Imports

import MWDATCore    // Registration, devices, permissions
import MWDATCamera  // Stream, VideoFrame, photo capture
import MWDATDisplay // Display, FlexBox, Text, Button, Image, Icon, VideoPlayer

For testing:

import MWDATMockDevice  // MockDeviceKit, MockGlasses, MockCameraKit

Key Types

• Wearables — SDK entry point. Call Wearables.configure() at launch, then use Wearables.shared (an any WearablesInterface)
• DeviceSession — The connection to a selected device. Create with createSession(deviceSelector:), then attach capabilities
• Camera — Camera capability from session.addCamera(config:); owns camera.stream
• Stream — Camera stream: start(), stop(), capturePhoto(format:), and the frame/state/photo/error publishers
• Display — Display capability from session.addDisplay()
• VideoFrame — Individual video frame with .makeUIImage() and .sampleBuffer
• Device / DeviceIdentifier — DeviceIdentifier is a String; resolve a Device with deviceForIdentifier(_:)
• AutoDeviceSelector — Selects the best available device, optionally filtered (filter: { $0.supportsDisplay() })
• SpecificDeviceSelector — Selects a specific device by DeviceIdentifier
• StreamConfiguration — Configure video codec, resolution, frame rate
• ListenerTokenBag / AnyListenerToken — Keep .listen {} subscriptions alive; dropping a token cancels it
• MockDeviceKit — Factory for creating simulated devices in tests

Error Handling

do {
    try Wearables.configure()
} catch {
    // Handle configuration error
}

do {
    try await Wearables.shared.startRegistration()
} catch {
    // Handle registration error
}

Build and Test

# Install dependencies via Swift Package Manager
# In Xcode: File > Add Package Dependencies > enter repo URL

# Build from command line
xcodebuild -scheme MWDATCore -destination 'platform=iOS Simulator,name=iPhone 16'

# Run tests
xcodebuild test -scheme MWDATCoreTests -destination 'platform=iOS Simulator,name=iPhone 16'

For sample apps:

# Open the sample app workspace
open ExternalSampleApps/CameraAccess/CameraAccess.xcodeproj

# Build and run on simulator (uses MockDeviceKit - no glasses needed)
xcodebuild -scheme CameraAccess -destination 'platform=iOS Simulator,name=iPhone 16'

Development Workflow

1. Add SDK via Swift Package Manager (SPM) in Xcode
2. Import modules (MWDATCore, MWDATCamera, MWDATDisplay when rendering Display content)
3. Configure at app launch: try Wearables.configure()
4. Build with Xcode or xcodebuild
5. Test with MockDeviceKit - no physical glasses required
6. Debug using Xcode console for SDK logs

Live docs search

If your editor supports remote MCP servers, connect https://mcp.developer.meta.com/wearables and use search_dat_docs for current DAT setup, session lifecycle, camera streaming, MockDeviceKit, permissions, and exact API symbols. This public docs server does not require authentication; do not configure tokens, OAuth, or custom authorization headers for it.

Use llms.txt when your tool only supports static reference context.

Links

• iOS API Reference
• Developer Documentation
• GitHub Repository