session(_:didUpdate:)

Notifies you when the session updates nearby objects.

Declaration

optional func session(_ session: NISession, didUpdate nearbyObjects: [NINearbyObject])

Parameters

session:
The session that updated.
nearbyObjects:
The array of nearby objects that the session updated.

Mentioned in

Initiating and maintaining a session

Discussion

Implement this callback to receive new nearby object updates for the argument session.

In Swift, if a peer is out of range or line of sight, the delegate reads the distance and direction as nil. An app can monitor this state and guide a person into range as necessary. For more information, see Initiating and maintaining a session.

In Objective-C, if a peer is out of range or line of sight, the delegate reads the distance as NINearbyObjectDistanceNotAvailable, and direction as NINearbyObjectDirectionNotAvailable.

An app can monitor this state and guide the user into range as necessary. For more information, see Initiating and maintaining a session.

Provide feedback based on proximity

Apps can react to positional information in an interaction session to create spatial awareness. For example, an app can play audio, invoke haptics, or display visual feedback when a peer is nearby. The following code calls two functions: it calls enableFunctionalityA when the device achieves a 1.5-meter proximity to the peer device, and enableFunctionalityB when the device achieves a 3-meter proximity to the peer device.

func session(_ session: NISession, didUpdate nearbyObjects: [NINearbyObject]) {
    // Ensure there's a current peer token.
    guard let peerToken = peerDiscoveryToken else {
        fatalError("don't have peer token")
    }

    // Find the right peer from session update.
    guard let peerObj = nearbyObjects.first (where: { $0.discoveryToken == peerToken }) else {
        return
    }

    // Retrieve the peer's distance, in meters.
    if let distance = peerObj.distance {
        // Compute peer object's distance.
    }
                
    // Retrieve the peer's horizontal angle, in radians.
    if let horizontalAngle = peerObj.horizontalAngle {
        // Compute peer object's angle.
    }

    // Retrieve the peer's direction, in `simd_float3`.
    if let direction = peerObj.direction {
        // Compute peer object's direction.
    }
}