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factorio-rs

State machines with enums

User-defined enums lower to tagged Lua tables. Use them for phases, commands, or any closed set of cases you want to match on - distinct from Factorio API string unions like GuiDirection.

Define the machine

Section titled “Define the machine”
enum Phase {
    Idle,
    Mining { ticks: i64 },
    Done,
}


impl Phase {
    fn tick(self) -> Phase {
        match self {
            Phase::Idle => Phase::Mining { ticks: 0 },
            Phase::Mining { ticks } if ticks + 1 >= 60 => Phase::Done,
            Phase::Mining { ticks } => Phase::Mining { ticks: ticks + 1 },
            Phase::Done => Phase::Done,
        }
    }
}

What Lua looks like

Section titled “What Lua looks like”
Rust Lua shape
Phase::Idle { tag = "Idle" }
Phase::Mining { ticks: 3 } { tag = "Mining", ticks = 3 }
Tuple variant Msg::Move(x, y) { tag = "Move", _1 = x, _2 = y }

Inherent methods share a table with unit variant constants, like structs.

Drive it from an event

Section titled “Drive it from an event”
use factorio_rs::prelude::*;


// Keep the current phase in storage or a local you refresh each event.
fn on_tick(phase: Phase) -> Phase {
    let next = phase.tick();
    match &next {
        Phase::Done => println!("finished"),
        Phase::Mining { ticks } => println!("mining t={ticks}"),
        Phase::Idle => {}
    }
    next
}

Persist the phase if it must survive saves - Persist with storage.

API string unions are different

Section titled “API string unions are different”
// Factorio literal union -> plain Lua string
let dir = GuiDirection::Horizontal; // "horizontal"

Your enum Phase is a tagged table. Do not mix the two mental models. Details: Enums.

See also

Section titled “See also”