dat-conventions

par facebook

Modèles Swift, async/await, conventions de nommage, types clés pour le développement iOS du SDK DAT

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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

Type	Convention	Example
Entry point	`Wearables.shared`	`Wearables.shared.startRegistration()`
Device sessions	`*Session`	`DeviceSession`
Capabilities	Named by function	`Stream`
Selectors	`*DeviceSelector`	`AutoDeviceSelector`, `SpecificDeviceSelector`
Config	`*Configuration`	`StreamConfiguration`
Publishers	`*Publisher`	`statePublisher`, `videoFramePublisher`

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

Add SDK via Swift Package Manager (SPM) in Xcode
Import modules (MWDATCore, MWDATCamera, MWDATDisplay when rendering Display content)
Configure at app launch: try Wearables.configure()
Build with Xcode or xcodebuild
Test with MockDeviceKit - no physical glasses required
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.

See the dat-docs-mcp skill for Claude Code, Cursor, and MCP Inspector setup and troubleshooting.

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