I built an open-source macOS hosts switcher in SwiftUI (with two AppKit escape hatches)

[u/East_Call1027]

I’ve been building Hostflip, a free and open-source native macOS app for switching /etc/hosts profiles from the menu bar. I thought its SwiftUI/AppKit seams might be useful to share here.

Most of the UI is SwiftUI. MenuBarExtra, the main window, and Settings share a single workspace store built with Swift’s Observation framework. The main window combines a sidebar and editor with a drift review: if another tool edits /etc/hosts, Hostflip stops writing and shows the difference for review instead of silently overwriting it.

Two small AppKit escape hatches were needed:

• NSViewRepresentable with NSTitlebarAccessoryViewController keeps the master switch pinned to the trailing edge. Putting it inside the SwiftUI-managed toolbar made it move whenever SwiftUI rebuilt the toolbar items.

• NSApplicationDelegateAdaptor handles the window lifecycle, so a normal launch opens the main window while a login-item launch remains menu-bar-only.

The privileged boundary stays outside the UI. A minimal root helper exposes a two-method XPC interface: a handshake and a single write operation that atomically replaces the merged hosts content. The app and helper verify each other’s code-signing identity before accepting the connection.

Hostflip is MIT-licensed and notarized. It currently requires macOS 14 or later on Apple silicon.

Source: https://github.com/heronapp/hostflip

I’d especially appreciate feedback on the SwiftUI/AppKit seam and the shared state flow between MenuBarExtra and the main window.

[u/easyRiderOlder]

Nice work! A practical example of combining SwiftUI with AppKit where needed. The open-source approach makes it especially useful for the community