SplitTimer

A native iOS split timer app built with SwiftUI — originally designed for timing golf cart laps, now general purpose for karting, running, or any activity where you want to track split times across multiple checkpoints.

Features

• Tracks & splits — create named tracks with custom split checkpoints (e.g. "T-intersection", "Back straight", "Lap 1")
• Live split timing — tap to split, times update at screen refresh rate via CADisplayLink
• Split colors — purple for overall best, green for personal best, yellow for slower
• Multi-runner support — name each run; personal bests are tracked per name
• History — all runs persisted to Firebase Firestore, synced across devices
• Haptic feedback — medium impact on each split, strong pulse on finish
• Screen always-on — idle timer disabled during active runs
• Background safe — timer stays accurate if app is backgrounded mid-run

Tech Stack

• SwiftUI — declarative UI, @Observable / @ObservedObject state management
• Firebase Firestore — NoSQL cloud database for cross-device persistence
• CADisplayLink — frame-rate display updates (~120fps on ProMotion) for smooth timer rendering
• UserDefaults — lightweight local persistence for runner name preference
• UIImpactFeedbackGenerator for haptics
• NotificationCenter for app lifecycle events

Architecture

ContentView (phase-based navigation)
├── HistoryView          — default screen, shows all runs across tracks
├── TrackPickerView      — select or create a track before running
└── RunView              — active timer, split list, finish sheet

Three view models handle all business logic:

• TimerViewModel — owns the CADisplayLink, split recording, and Firestore write
• TrackViewModel — track + split definition CRUD, Firestore read/write
• HistoryViewModel — loads all runs with splits, computes best times per split definition

Data model:

Track
  └── [SplitDefinition]   id, name, order

Run
  └── [Split]             split_at timestamp, split_def_id FK

Tracks own their split definitions as an embedded array in Firestore. Runs and splits are separate top-level collections, with splits fetched and joined client-side after loading runs.

Data Flow

TrackPickerView → select track
    → TimerViewModel(track) initialized with track's SplitDefinitions
    → user taps Start → CADisplayLink begins, startTime = Date()
    → each Split tap → Split(Date(), run.id, splitDef.id) appended
    → finish → timestamps recorded, Firestore write, history reloads

Setup

1. Clone the repo
2. Create a Firebase project at console.firebase.google.com
3. Add an iOS app, download GoogleService-Info.plist, add to Xcode target
4. Enable Firestore in Firebase console (test mode is fine to start)
5. Add Firebase SDK via SPM: https://github.com/firebase/firebase-ios-sdk
6. Build & run

Firestore Collections

Collection	Key fields
tracks	name, created_at, splits[] (embedded)
runs	track_id, user_name, started_at, ended_at
splits	run_id, split_def_id, split_at

Potential Next Steps

• Auth (Firebase Auth) to replace name-based personal bests with real user accounts
• Firestore security rules scoped per user
• Live leaderboard view per track
• Apple Watch companion for wrist-tap splits
• Export run data to CSV