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0.2.0 Dec 9, 2019
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#1014 in Procedural macros

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Used in 3 crates

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11KB
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#[derive(Defaults)]

A better Default derive macro.

Crate

Examples:

You can provide default value for a non-default field.

#[derive(Defaults)]
pub struct Event {
    id: usize,
    name: String,
    #[def = "Instant::now()"]
    time: Instant,
}

You can also provide a different default value of an already default field.

#[derive(Defaults)]
pub struct Event {
    #[def = "4"]
    id: usize,
    name: String,
    #[def = "Instant::now()"]
    time: Instant,
}

You can even provide default value of enums:

#[derive(Defaults)]
#[def = "A"]
pub struct Classroom {
    A,
    B,
    C
}

But what about variants with data?

#[derive(Defaults)]
#[def = "A(100)"]
pub struct SomeEnum {
    A(usize),
    B { x: usize, y: usize },
    C
}

Dependencies

~1.5MB
~34K SLoC