GitInflow went from idea to App Store in a single sprint. Here's a look at the key technical decisions we made along the way.

Architecture: SwiftUI + MVVM + No Backend

The entire app runs on two things: SwiftUI and the GitHub REST API. No custom backend, no database, no sync engine.

SwiftUI Views
  → ViewModels (@MainActor, ObservableObject)
    → Services (GitHubAPIClient, StatusService, CacheService)
      → GitHub REST API v3

This simplicity is intentional. Every piece of data lives on GitHub. The app is just a view layer with local caching.

Kanban via Labels

The kanban system uses GitHub labels (status:ready, status:inProgress, status:done) instead of GitHub Projects. Why?

1. No API complexity — Labels are a single field on the Issue object
2. Universal — Works with any GitHub client, CLI tool, or automation
3. Auto-creation — GitInflow creates missing labels on first use via POST /repos/{owner}/{repo}/labels

When you move an issue to "Done", the app does two things in sequence: updates the labels, then closes the issue. Moving back reopens it.

Multi-Repository: TaskGroup for Parallel Fetching

One of the most impactful features is viewing issues across up to 5 repositories at once. This is implemented with Swift's withTaskGroup:

await withTaskGroup(of: (Repository, Result<[Issue], Error>).self) { group in
    for repo in repos {
        group.addTask {
            do {
                var fetched = try await self.apiClient.fetchIssues(...)
                // Filter PRs, assign repoFullName
                return (repo, .success(fetched))
            } catch {
                return (repo, .failure(error))
            }
        }
    }
    // Merge results, track failures
}

Partial failures are tracked separately — if one repo fails, the others still display. An error banner shows which repo failed with a retry button.

OAuth Security: Server-Side Token Exchange

The initial implementation had the OAuth client secret embedded in the app binary. This is a common pattern but fundamentally insecure — anyone can extract it with strings.

We moved token exchange to a Cloudflare Worker:

App → sends auth code → Cloudflare Worker → exchanges for token → returns token to app

The worker holds the client secret via wrangler secret. The app never sees it. Total cost: $0 (Cloudflare free tier).

Share Extension: App Group + Keychain Sharing

The Share Extension runs as a separate process. It needs two things from the main app:

1. OAuth token — Shared via Keychain Access Group
2. Selected repositories — Shared via App Group UserDefaults

This required careful entitlement configuration:

• Both targets need keychain-access-groups with $(AppIdentifierPrefix)com.gitinflow.GitInflow
• Both targets need com.apple.security.application-groups with group.com.gitinflow.shared

Localization: String Catalogs

Rather than maintaining .strings files, we use Xcode's String Catalog format (.xcstrings). SwiftUI's Text("日本語") automatically looks up translations in the catalog — no code changes needed for most strings.

For non-SwiftUI contexts (error messages, notifications), we use String(localized:).

Widget: WidgetKit + App Group

The widget reads issue counts from App Group UserDefaults. The main app writes these counts after each fetch:

private func updateWidgetData() {
    let defaults = UserDefaults(suiteName: AppConfig.appGroupID)
    defaults?.set(backlogCount, forKey: "widget_backlog_count")
    // ...
    WidgetCenter.shared.reloadAllTimelines()
}

Simple, reliable, no background networking required.

What We'd Do Differently

• Pagination from day one — We added it later, but the 100-item limit bit us early in testing
• Protocol-first services — We retrofitted StatusServiceProtocol and AuthServiceProtocol; should have started with them
• Offline support — Not yet implemented, but the caching infrastructure is there

Stack Summary

Component	Technology
UI	SwiftUI (iOS 17+)
Architecture	MVVM + @MainActor
Networking	URLSession + async/await
Concurrency	TaskGroup (parallel fetch)
Auth	OAuth + Cloudflare Workers
Storage	Keychain (tokens), UserDefaults (preferences)
Extensions	Share Extension, WidgetKit
Localization	String Catalogs (.xcstrings)
Build	xcodegen (project.yml)

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Interested in the code? GitInflow is built in the open. Questions and feedback welcome at gitinflow@hakaru.net.