Crate thisenum

thisenum

The simplest way to assign constant literals to enum arms in Rust! What fun!

Please also see enum-assoc, which is a more robust alternative.

use thisenum::Const;

#[derive(Const, Debug)]
#[armtype(&[u8])]
/// https://exiftool.org/TagNames/EXIF.html
enum ExifTag {
    // ...
    #[value = b"\x01\x00"]
    ImageWidth,
    #[value = b"\x01\x01"]
    ImageHeight,
    #[value = b"\x01\x02"]
    BitsPerSample,
    #[value = b"\x01\x03"]
    Compression,
    #[value = b"\x01\x06"]
    PhotometricInterpretation,
    // ...
}

assert_eq!(ExifTag::ImageWidth.value(), b"\x01\x00");
#[cfg(feature = "eq")]
assert_eq!(ExifTag::ImageWidth, b"\x01\x00");

If each arm is a different type, this is still possible using ConstEach:

use thisenum::ConstEach;

#[derive(ConstEach, Debug)]
enum CustomEnum {
    #[armtype(&[u8])]
    #[value = b"\x01\x00"]
    A,
    // `armtype` is not required, type is inferred
    #[value = "foo"]
    B,
    #[armtype(f32)]
    #[value = 3.14]
    C,
}

assert_eq!(CustomEnum::A.value::<&[u8]>().unwrap(), b"\x01\x00");
assert!(CustomEnum::B.value::<&str>().is_some());
assert_eq!(CustomEnum::B.value::<&str>().unwrap(), &"foo");
assert_eq!(CustomEnum::B.value::<&str>(), Some("foo").as_ref());
assert_eq!(CustomEnum::C.value::<f32>().unwrap(), &3.14);
// or on failure
assert!(CustomEnum::C.value::<i32>().is_none());

License

thisenum is released under the MIT License http://opensource.org/licenses/MIT.

Enums

Error

All errors that can occur while using TryFrom implementation for Const

Derive Macros

Const

Add’s constants to each arm of an enum

ConstEach

Add’s constants of any type to each arm of an enum