Default

The Default derive macro generates an impl Default for your struct, with per-field custom default values. Annotate fields with #[moxy(default = expr)] to override the standard Default::default().

When imported via use moxy::Default, this derive shadows std’s built-in Default derive. Fields without #[moxy(default = ...)] still receive their normal Default::default() value.

Note

use moxy::Default shadows Rust’s built-in Default derive. If you need both in the same module, qualify the std one explicitly: #[derive(std::default::Default)].

Basic Usage

use moxy::Default;

#[derive(Default)]
struct Config {
    #[moxy(default = "localhost")]
    pub host: String,
    #[moxy(default = 8080u16)]
    pub port: u16,
    pub debug: bool,
}

let config = Config::default();
assert_eq!(config.host, "localhost");
assert_eq!(config.port, 8080);
assert_eq!(config.debug, false); // standard Default::default()

What Gets Generated

The macro generates a standard impl Default for Config block. Each annotated field uses its expression (passed through .into()), while unannotated fields fall back to Default::default():

impl Default for Config {
    fn default() -> Self {
        Self {
            host: "localhost".into(),
            port: 8080u16.into(),
            debug: Default::default(),
        }
    }
}

When to Use

Use moxy’s Default instead of std’s when you need per-field default values without writing the impl block by hand. For structs where every field is fine with its type’s Default::default(), std’s built-in derive is sufficient.

What’s Next

• Expressions — literals, constants, method calls, and Into<T> coercion
• Struct Types — named structs, tuple structs, unit structs, and generics