Core Bluetooth

What to open

• Use corebluetooth/AboutCoreBluetooth.md and corebluetooth/CoreBluetoothOverview.md for concepts and role orientation.
• Use corebluetooth/PerformingCommonCentralRoleTasks.md for step-by-step central workflows.
• Use corebluetooth/PerformingCommonPeripheralRoleTasks.md for step-by-step peripheral workflows.
• Use corebluetooth/BestPracticesforInteractingwithaRemotePeripheralDevice.md and corebluetooth/BestPracticesforSettingUpYourLocalDeviceasaPeripheral.md for pitfalls and best practices.
• Use corebluetooth/CoreBluetoothBackgroundProcessingforiOSApps.md for background modes and lifecycle constraints.
• Use corebluetooth/corebluetooth.md for API quick maps and symbol lookup.

Workflow

• Identify whether the app acts as a central, a peripheral, or both.
• Wait for the manager state to be poweredOn before issuing BLE operations.
• Follow the role checklist to keep discovery and connection order correct.
• Open the role task guide and best practices first; use the API reference for exact signatures.

Central checklist

1. Create a CBCentralManager with a delegate and queue.
2. Handle centralManagerDidUpdateState(_:) and gate scanning on .poweredOn.
3. Scan with scanForPeripherals(withServices:options:) and stop when the target is found.
4. Connect, set the CBPeripheral delegate, and discover services and characteristics.
5. Read, write, or subscribe to characteristic notifications as needed.

Peripheral checklist

1. Create a CBPeripheralManager with a delegate and queue.
2. Wait for the state to become .poweredOn.
3. Define services and characteristics, then add them to the manager.
4. Start advertising with service UUIDs and optional local name.
5. Respond to read and write requests; publish updates to subscribed centrals.

Reminders

• Retain discovered CBPeripheral instances to keep them alive.
• Use notifications for streaming data; use write-without-response only when canSendWriteWithoutResponse is true.
• Use L2CAP only for use cases that do not fit GATT characteristics.