rust 14 lines · 1 tab

Default trait for sensible zero values

Marcus Chen Jan 2026

1 tab

#[derive(Default, Debug)]
struct Config {
    host: String,
    port: u16,
    debug: bool,
}

fn main() {
    let config = Config {
        port: 8080,
        ..Default::default()
    };
    println!("{:?}", config);
}

1 file · rust Explain with highlit

The Default trait provides a default value for a type, useful for builder patterns, config merging, and initialization. I derive Default on structs where zero/empty is meaningful. For custom logic, implement it manually. Default::default() is the standard way to create an instance. It's especially useful with struct update syntax: Config { port: 8080, ..Default::default() }. For types like Vec, String, and Option, default is already implemented (empty vec, empty string, None). I use Default bounds in generic code when I need to create instances. It's a small convenience that makes APIs more ergonomic and composable.

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