Fullo Sustainable Code Skill Setup Gc Mobile IOS

Green Coding — iOS

Audit an iOS app for energy efficiency, battery impact, and sustainability.

When to use

• Auditing an iOS/iPadOS/watchOS app for energy consumption
• Investigating battery drain complaints
• Reviewing Swift/SwiftUI/UIKit code for green patterns
• Measuring SCI for a mobile operation (API call, screen render, background task)

MCP tools (optional)

If the sustainable-code MCP server is configured:

Workflow

iOS Green Audit Progress:
- [ ] Phase 1: Explore — understand architecture and energy profile
- [ ] Phase 2: Energy profiling — identify battery-draining operations
- [ ] Phase 3: Code patterns — check against Creedengo iOS rules
- [ ] Phase 4: Network efficiency — minimize data transfer
- [ ] Phase 5: Asset optimization — reduce resource footprint
- [ ] Phase 6: SCI measurement — quantify carbon per operation
- [ ] Phase 7: Report and recommendations

Phase 1 — Explore

Understand the app's architecture and energy profile:

• Language: Swift, Objective-C, or mixed?
• UI framework: SwiftUI, UIKit, or hybrid?
• Architecture: MVC, MVVM, TCA, VIPER?
• Dependencies: CocoaPods, SPM, Carthage? How many?
• Background tasks: push notifications, background fetch, location tracking?
• Network layer: URLSession, Alamofire, custom?
• Persistence: Core Data, SwiftData, Realm, SQLite, UserDefaults?
• Media: camera, video, audio processing?
• Sensors: GPS, accelerometer, Bluetooth, NFC?

Phase 2 — Energy profiling

Identify the biggest energy consumers. On iOS, the main energy drains are:

Measurement tools

Recommend the user profile their app using:

1. Xcode Energy Gauge (Product → Profile → Energy Impact) — real-time energy score (0-20 scale) during development
2. Xcode Instruments — Energy Log — detailed per-subsystem breakdown (CPU, GPU, network, location, Bluetooth)
3. MetricKit — production energy metrics from real users (iOS 13+):

   // Add MXMetricManagerSubscriber to receive daily energy reports
   class MetricsSubscriber: NSObject, MXMetricManagerSubscriber {
       func didReceive(_ payloads: [MXMetricPayload]) {
           // payloads contain cumulativeCellularConditionTime,
           // cumulativeWiFiConditionTime, cpuMetrics, gpuMetrics
       }
   }
   

4. Xcode Organizer → Energy — aggregated energy data from App Store users

Phase 3 — Code patterns (Creedengo iOS rules)

Check Swift files against Creedengo iOS energy rules:

Use the creedengo_check MCP tool on Swift files, or manually review against these patterns.

Additionally check for general Swift energy patterns:

• Prefer struct over class — value types avoid heap allocation and ARC overhead
• Avoid DispatchQueue.main.async flooding — batch UI updates
• Use lazy var for expensive computed properties
• Prefer async/await over completion handler chains — cleaner, avoids retain cycles
• Use URLSession background transfers for large downloads instead of foreground requests

Phase 4 — Network efficiency

Mobile network operations are energy-expensive. Check:

Phase 5 — Asset optimization

Phase 6 — SCI measurement

Measure the carbon intensity of key operations:

1. Choose functional units: "per API call", "per screen render", "per background sync"
2. Measure wall-clock time using CFAbsoluteTimeGetCurrent() or ContinuousClock:

   let clock = ContinuousClock()
   let duration = try await clock.measure {
       // operation to measure
   }
   let wallTimeMs = duration.components.seconds * 1000
       + duration.components.attoseconds / 1_000_000_000_000_000
   

3. Get grid carbon intensity via grid_carbon_intensity MCP tool (use user's region)
4. Calculate SCI via sci_calculate MCP tool:
   • wallTimeMs: measured duration
   • devicePowerW: ~3W (iPhone average) or ~5W (iPad)
   • carbonIntensity: from step 3
   • embodiedTotalG: ~70000 (iPhone, from Apple Environmental Report)
   • lifetimeHours: ~26280 (3 years typical iPhone lifecycle)

Phase 7 — Report

## iOS Green Audit: [app name]

### Energy profile
| Component | Impact | Status | Notes |
|-----------|--------|--------|-------|
| Location | high/medium/low/none | ok/warn/fail | ... |
| Networking | ... | ... | ... |
| CPU/processing | ... | ... | ... |
| Graphics/GPU | ... | ... | ... |
| Sensors | ... | ... | ... |
| Background tasks | ... | ... | ... |

### Code patterns (Creedengo iOS)
| File | Rule violated | Severity | Fix |
|------|--------------|----------|-----|
| ... | ... | high/medium/low | ... |

### SCI measurements
| Operation | SCI (mgCO2eq) | Notes |
|-----------|---------------|-------|
| ... | ... | ... |

### Top 5 Recommendations
1. [highest impact action]
2. ...

### Methodology and sources
- Formula: SCI = ((E x I) + M) / R — [GSF SCI Specification v1.0](https://sci-guide.greensoftware.foundation/) (ISO 21031:2024)
- Code rules: [Creedengo iOS](https://github.com/green-code-initiative/creedengo-ios) — green-code-initiative
- Energy profiling: Xcode Instruments Energy Log / MetricKit
- Device power: [value] W — Apple Product Environmental Report [year]
- Embodied carbon: [value] gCO2eq — [Apple Product Environmental Report](https://www.apple.com/environment/) [year]
- Grid carbon intensity: [value] gCO2eq/kWh — [Ember Global Electricity Review](https://ember-energy.org/) [year]
- Platform guide: [Apple Energy Efficiency Guide for iOS Apps](https://developer.apple.com/library/archive/documentation/Performance/Conceptual/EnergyGuide-iOS/)

Gotchas

• Xcode Energy Gauge is not available in simulators: Energy profiling requires a physical device. Always test energy on real hardware, not the iOS Simulator.
• MetricKit reports are daily aggregates: You cannot get real-time energy data from MetricKit. For granular measurement during development, use Xcode Instruments instead.
• Battery percentage is not a valid energy metric: Battery drain depends on total capacity, charge cycles, ambient temperature, and other apps. Use Xcode's energy score (0-20) or MetricKit cumulative metrics instead.
• Background app refresh varies by user settings: Users can disable background refresh per-app. Don't assume your background tasks always run — and don't over-schedule as backup.

Post-report verification

After presenting the iOS audit report, automatically run /gc-verify in quick mode. This triggers a Chain-of-Verification (CoVe) process: extract claims from the report, generate adversarial questions, answer each independently, and present findings under a ## Verification (CoVe) heading.

Related commands

• /gc-mobile-android — green coding audit for Android apps
• /gc-setup — full 9-phase sustainability audit (web-focused)
• /gc-measure-sci — measure SCI for any operation
• /gc-dev — daily development companion

Source: fullo/sustainable-code-skill-setup — distributed by TomeVault.