Settings that change gameplay

Use a settings-stage mod_settings! plus a control-stage read so players can toggle behavior without editing code.

1. Declare the setting

src/settings.rs (or settings_mod! in lib.rs):

use factorio_rs::prelude::*;

factorio_rs::mod_settings! {
    prefix = "my_mod",

    startup {
        casual_mode: bool = false,
    }
}

This generates Settings::CASUAL_MODE and a register() entry point Factorio calls at settings load. Details: Mod settings.

2. Read it in control

use factorio_rs::prelude::*;
use crate::settings::Settings;

fn casual_mode() -> bool {
    settings.startup.get_bool(Settings::CASUAL_MODE)
}

#[factorio_rs::event(OnSingleplayerInit)]
pub fn on_singleplayer_init() {
    if casual_mode() {
        println!("casual mode on");
    } else {
        println!("casual mode off");
    }
}

3. Localize the label (optional)

factorio_rs::locale! {
    en {
        ["mod-setting-name.my_mod-casual-mode"] = "Casual mode",
        ["mod-setting-description.my_mod-casual-mode"] = "Softer defaults for new players.",
    }
}

See Locale.

4. Cover the branch with a test

Startup settings are fixed for a test run’s mod config. Assert the branch you care about after arranging the setting in Factorio’s test harness, or keep the helper pure and unit-test the decision:

fn welcome(casual: bool) -> &'static str {
    if casual { "casual mode on" } else { "casual mode off" }
}

#[cfg(test)]
mod tests {
    use super::welcome;

    #[test]
    fn welcome_respects_flag() {
        assert_eq!(welcome(true), "casual mode on");
        assert_eq!(welcome(false), "casual mode off");
    }
}

For world-touching checks, use factorio-rs test - Testing.

See also

• First hour - scaffold -> build -> test loop
• mandatory_spaghetti - settings + locale in a larger mod