Three Levels, One Path

Can you open Harbor → v1.4.0 → build 418 without three taps?

With a value-typed path you can: one write, three levels. With tap-only NavigationLinks and no path binding, you cannot — and a relaunch will not remember where you were either. This bench puts both next to each other and prints the depth on the cards.

Root — both at zero

PATH is a NavigationStack(path:) over [ShipRoute]. LINKS is a NavigationStack with nested links and no path binding — the control.

Deep — one append, three levels

path = [.app, .version, .build]  // Harbor › v1.4.0 › build 418
// Links has no path to write — depth stays 0

Same moment, same screen. The mint card moved; the rose card did not.

Pop — clear the array

path = []  // removeAll — back to root

Observed: PATH 0, tape [], phase POP, status removeAll. LINKS was already at root.

Save, then relaunch

Seed mode deep-links, then writes the encoded [ShipRoute] to UserDefaults. Observed: PHASE SAVED, PATH 3, LINKS 0, status defaults ← path.

A fresh process with -mode reload reads the array back into path. Observed: PHASE RESTORED, PATH 3, tape Harbor › v1.4.0 › build 418, LINKS 0, status path ← defaults.

Mini-exercise

Change deepPath to only [.app, .version]. Re-run seed → reload. Confirm PATH settles at 2 and the tape stops at v1.4.0.

Challenges

1. Swap [ShipRoute] for a NavigationPath and deep-link a second type (e.g. a review id) beside ShipRoute.
2. Add a "Pop one" button that does path.removeLast() and photograph depth 3 → 2 → 1.
3. Drive the same path from a simulated URL (harbor/v1.4.0/418) parsed into [ShipRoute].
4. Put the bench back inside an outer NavigationStack and photograph how the destination steals the window — then fix it the way Launch Lab does for -bench launches.
5. XCUITest: after -mode reload, assert static text contains RESTORED and PATH 3.

Key Points

• NavigationStack(path:) shares stack state with your code.
• Observed deep-link: PATH 3 / LINKS 0 for Harbor › v1.4.0 › build 418.
• Observed pop: PATH 0, status removeAll.
• Observed relaunch: PHASE RESTORED, PATH 3, LINKS 0.
• navigationDestination(for:) maps values to screens for taps and appends alike.
• Nested NavigationLinks without a path cannot be deep-linked or restored.
• An outer NavigationStack around a path-bound bench can swallow pushes — direct -bench launch avoids that.
• Chapter 13's lesson applies: if you want a relaunch to wake deep, persist the path.

Next up: gestures — drag, long-press, and simultaneous/sequenced composition, with a live readout of which gesture won — including scroll-vs-drag as the control.