2 releases

0.1.2 Oct 7, 2021
0.1.1 Oct 1, 2021
0.1.0 Oct 1, 2021

#803 in Rust patterns

BSD-3-Clause

6KB

Zhi Enum

Easily create casting traits with unknown field support.

Usage

  1. Add EnumConvert or EnumTryConvert into the derive attribute.
use zhi_enum::{EnumConvert, EnumTryConvert};

#[derive(Debug, Ord, PartialOrd, Eq, PartialEq, EnumConvert)]
#[repr(u8)]
enum NumberConvert {
    Zero,
    One,
    Two,
    Three,
    Four,
    Ten = 10,
    Eleven,
    Twenty = 10 + 10,
    TwentyOne,
    #[zhi_enum(unknown)]
    Unknown(u8),
}

#[derive(Debug, Ord, PartialOrd, Eq, PartialEq, EnumTryConvert)]
#[repr(u8)]
enum NumberTryConvert {
    Zero,
    One,
    Two,
    Three,
    Four,
    Ten = 10,
    Eleven,
    Twenty = 10 + 10,
    TwentyOne,
    #[zhi_enum(unknown)]
    Unknown(u8),
}

  1. Then, you can use .from/.into convert functions
assert_eq!(NumberConvert::Three.into_u8(), 3u8);
assert_eq!(NumberTryConvert::Three.try_into_u8().unwrap(), 3u8);
assert_eq!(NumberConvert::Ten.into_u8(), 10u8);
assert_eq!(NumberTryConvert::Ten.try_into_u8().unwrap(), 10u8);
assert_eq!(NumberConvert::Eleven.into_u8(), 11u8);
assert_eq!(NumberTryConvert::Eleven.try_into_u8().unwrap(), 11u8);
assert_eq!(NumberConvert::TwentyOne.into_u8(), 21u8);
assert_eq!(NumberTryConvert::TwentyOne.try_into_u8().unwrap(), 21u8);

assert_eq!(NumberConvert::from(3u8), NumberConvert::Three);

use std::convert::TryFrom;
assert_eq!(NumberTryConvert::try_from(21u8).unwrap(), NumberTryConvert::TwentyOne);

Handle unknown discriminant

  • If you have defined a variant with #[zhi_enum(unknown)] attribute in your enum like this :

    #[zhi_enum(unknown)]
    Whatever(repr type),
    

    which the repr type is the represented type as you define use #[repr(...)].

    Then, when you convert a repr type into enum type, an unknown discriminant will be converted to this variant with its unknown value.

  • If you have not defined, the .try_into() will returns Err(UnknownVariantError{}), and the .into() will call panic!.

FAQ

  • Error E0658

    If you get this error:

    error[E0658]: custom discriminant values are not allowed in enums with tuple or struct variants
      --> <source>:2:9
    

    It means that your rustc version is lower than 1.56.

    You can just upgrade your rustc. Or if you don't want upgrade, you have to add #![feature(arbitrary_enum_discriminant)] to your project.

License

BSD-3-Clause

Dependencies

~265–670KB
~16K SLoC