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Save games

· One min read
Dragos
Balaur

save::write(slot, data) and save::read(slot): a table per user, written so a crash cannot truncate it, and migrated when the game moves on.

What landed​

  • Slots. A slot is a name — letters, digits, - and _ — checked rather than trusted. save::slots() lists them and save::remove(slot) deletes one. Files live under the platform's user-data directory, so game code never hardcodes an OS path.
  • Atomic. A file is written beside its target and renamed over it, so a crash mid-save leaves the previous file whole.
  • Versioned. Every file carries the build's [save] version. Reading an older one calls the migration script's migrate_save(version, data) once per version step — 1 to 2, then 2 to 3 — so a migration only knows how the shape changed between two adjacent versions. A file from a newer build is refused rather than misread.
# project.toml
[save]
version = 3
migrate = "scripts/saves.rn"
save::write("slot1", #{ level: 4, coins: 120 });
let data = save::read("slot1");

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