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macro smart-default

Rust custom-derive macro for Default with more control on the fields

10 releases (6 breaking)

0.7.1 Apr 24, 2023
0.6.0 Dec 13, 2019
0.5.2 Apr 13, 2019
0.5.1 Mar 1, 2019
0.2.0 Aug 21, 2017

#36 in Procedural macros

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Used in 266 crates (88 directly)

MIT license

15KB
251 lines

Build Status Latest Version Rust Documentation

Rust SmartDefault

Custom derive for automatically implementing the Default trait with customized default values:

use smart_default::SmartDefault;

#[derive(SmartDefault)]
enum Foo {
    Bar,
    #[default]
    Baz {
        #[default = 12]
        a: i32,
        b: i32,
        #[default(Some(Default::default()))]
        c: Option<i32>,
        #[default(_code = "vec![1, 2, 3]")]
        d: Vec<u32>,
        #[default = "four"]
        e: String,
    },
    Qux(i32),
}

assert!(Foo::default() == Foo::Baz {
    a: 12,
    b: 0,
    c: Some(0),
    d: vec![1, 2, 3],
    e: "four".to_owned(),
});

Requires Rust 1.30+ (for non-string values in attributes)

Dependencies

~310–760KB
~18K SLoC