The iOS app is a SwiftUI application that interfaces with the Haskell core library via FFI. It shares the SimpleXChat framework with two extensions: Notification Service Extension (NSE) for push notifications and Share Extension (SE) for sharing content from other apps.

Build & Development

Open SimpleX.xcodeproj in Xcode. The project has five targets:

SimpleX (iOS) - Main app (Bundle ID: chat.simplex.app)
SimpleXChat - Framework containing FFI bridge and shared types
SimpleX NSE - Notification Service Extension
SimpleX SE - Share Extension
Tests iOS - UI tests

Build and run via Xcode (Product > Build/Run). Tests run via Product > Test or:

xcodebuild test -scheme "SimpleX (iOS)" -destination 'platform=iOS Simulator,name=iPhone 15'

Deployment target: iOS 15.0+, Swift 5.0.

Architecture

Haskell Core Integration

The app calls the Haskell core library through C FFI defined in SimpleXChat/SimpleX.h:

chat_migrate_init_key() - Initialize/migrate database
chat_send_cmd_retry() - Send command to chat controller
chat_recv_msg_wait() - Receive messages from controller

Swift wrappers in SimpleXChat/API.swift:

chatMigrateInit() - Initialize chat controller
sendSimpleXCmd<R>() - Send typed commands and parse responses
recvSimpleXMsg<R>() - Receive typed messages

Haskell runtime initialization (SimpleXChat/hs_init.c) uses different memory configurations:

Main app: 64MB heap
NSE: 512KB heap (minimal footprint for background processing)
SE: 1MB heap

Pre-compiled Haskell libraries are in Libraries/{ios,mac,sim}/.

State Management

ChatModel (Shared/Model/ChatModel.swift) - Main singleton ObservableObject for app-wide state (chat list, active chat, users)
ItemsModel - Manages chat items within a selected chat (similar to Kotlin's ChatsContext)
AppTheme - Theme management and customization

App Structure

Entry point: Shared/SimpleXApp.swift

Key directories in Shared/:

Model/ - Data models and API layer (ChatModel.swift, SimpleXAPI.swift)
Views/ - SwiftUI views organized by feature:
- ChatList/ - Chat list and user picker
- Chat/ - Message display and composition
- Call/ - VoIP call UI
- UserSettings/ - App settings
- LocalAuth/ - Passcode and biometric authentication
- Database/ - Database initialization and migration

Shared Data Between Targets

All three targets share data via App Group (group.chat.simplex.app):

SimpleXChat/AppGroup.swift - GroupDefaults wrapper for typed shared preferences
Keychain for sensitive data: kcDatabasePassword, kcAppPassword, kcSelfDestructPassword

Key Types

Types are defined in SimpleXChat/:

ChatTypes.swift - User, Chat, Message, Group types
APITypes.swift - API request/response types

Commands follow ChatCmdProtocol (has cmdString property), sent as JSON through FFI.

Localization

31 languages supported. Localization files in SimpleX Localizations/.

Workflow:

Product > Export Localizations - Export XLIFF files
Product > Import Localizations - Import updated translations

Background Capabilities

Configured in Info.plist:

Background modes: audio, fetch, remote-notification, voip
URL scheme: simplex:// for deep linking
BGTaskScheduler: chat.simplex.app.receive