Core Location Patterns

Discipline skill for Core Location implementation decisions. Prevents common authorization mistakes, battery drain, and background location failures.

When to Use

• Choosing authorization strategy (When In Use vs Always)
• Deciding monitoring approach (continuous vs significant-change vs CLMonitor)
• Implementing geofencing or background location
• Debugging "location not working" issues
• Reviewing location code for anti-patterns

Related Skills

• axiom-core-location-ref — API reference, code examples
• axiom-core-location-diag — Symptom-based troubleshooting
• axiom-energy — Location as battery subsystem

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Part 1: Anti-Patterns (with Time Costs)

Anti-Pattern 1: Premature Always Authorization

Wrong (30-60% denial rate):

// First launch: "Can we have Always access?"
manager.requestAlwaysAuthorization()

Right (5-10% denial rate):

// Start with When In Use
CLServiceSession(authorization: .whenInUse)

// Later, when user triggers background feature:
CLServiceSession(authorization: .always)

Time cost: 15 min to fix code, but 30-60% of users permanently denied = feature adoption destroyed.

Why: Users deny aggressive requests. Start minimal, upgrade when user understands value.

---

Anti-Pattern 2: Continuous Updates for Geofencing

Wrong (10x battery drain):

for try await update in CLLocationUpdate.liveUpdates() {
    if isNearTarget(update.location) {
        triggerGeofence()
    }
}

Right (system-managed, low power):

let monitor = await CLMonitor("Geofences")
let condition = CLMonitor.CircularGeographicCondition(
    center: target, radius: 100
)
await monitor.add(condition, identifier: "Target")

for try await event in monitor.events {
    if event.state == .satisfied { triggerGeofence() }
}

Time cost: 5 min to refactor, saves 10x battery.

---

Anti-Pattern 3: Ignoring Stationary Detection

Wrong (wasted battery):

for try await update in CLLocationUpdate.liveUpdates() {
    processLocation(update.location)
    // Never stops, even when device stationary
}

Right (automatic pause/resume):

for try await update in CLLocationUpdate.liveUpdates() {
    if let location = update.location {
        processLocation(location)
    }
    if update.isStationary, let location = update.location {
        // Device stopped moving - updates pause automatically
        // Will resume when device moves again
        saveLastKnownLocation(location)
    }
}

Time cost: 2 min to add check, saves significant battery.

---

Anti-Pattern 4: No Graceful Denial Handling

Wrong (broken UX):

for try await update in CLLocationUpdate.liveUpdates() {
    guard let location = update.location else { continue }
    // User denied - silent failure, no feedback
}

Right (graceful degradation):

for try await update in CLLocationUpdate.liveUpdates() {
    if update.authorizationDenied {
        showManualLocationPicker()
        break
    }
    if update.authorizationDeniedGlobally {
        showSystemLocationDisabledMessage()
        break
    }
    if let location = update.location {
        processLocation(location)
    }
}

Time cost: 10 min to add handling, prevents confused users.

---

Anti-Pattern 5: Wrong Accuracy for Use Case

Wrong (battery drain for weather app):

// Weather app using navigation accuracy
CLLocationUpdate.liveUpdates(.automotiveNavigation)

Right (match accuracy to need):

// Weather: city-level is fine
CLLocationUpdate.liveUpdates(.default)  // or .fitness for runners

// Navigation: needs high accuracy
CLLocationUpdate.liveUpdates(.automotiveNavigation)

Use Case	Configuration	Accuracy	Battery
Navigation	.automotiveNavigation	~5m	Highest
Fitness tracking	.fitness	~10m	High
Store finder	.default	~10-100m	Medium
Weather	.default	~100m+	Low

Time cost: 1 min to change, significant battery savings.

---

Anti-Pattern 6: Not Stopping Updates

Wrong (battery drain, location icon persists):

func viewDidLoad() {
    Task {
        for try await update in CLLocationUpdate.liveUpdates() {
            updateMap(update.location)
        }
    }
}
// User navigates away, updates continue forever

Right (cancel when done):

private var locationTask: Task<Void, Error>?

func startTracking() {
    locationTask = Task {
        for try await update in CLLocationUpdate.liveUpdates() {
            if Task.isCancelled { break }
            updateMap(update.location)
        }
    }
}

func stopTracking() {
    locationTask?.cancel()
    locationTask = nil
}

Time cost: 5 min to add cancellation, stops battery drain.

---

Anti-Pattern 7: Ignoring CLServiceSession (iOS 18+)

Wrong (procedural authorization juggling):

func requestAuth() {
    switch manager.authorizationStatus {
    case .notDetermined:
        manager.requestWhenInUseAuthorization()
    case .authorizedWhenInUse:
        if needsFullAccuracy {
            manager.requestTemporaryFullAccuracyAuthorization(...)
        }
    // Complex state machine...
    }
}

Right (declarative goals):

// Just declare what you need - Core Location handles the rest
let session = CLServiceSession(authorization: .whenInUse)

// For feature needing full accuracy
let navSession = CLServiceSession(
    authorization: .whenInUse,
    fullAccuracyPurposeKey: "Navigation"
)

// Monitor diagnostics if needed
for try await diag in session.diagnostics {
    if diag.authorizationDenied { handleDenial(