Derive Macro EnumRepr

#[derive(EnumRepr)]
{
    // Attributes available to this derive:
    #[enum_repr]
}

Automatically implements [std::convert::From] for repr from enum. And implements [std::convert::TryFrom] for enum from repr. or implements [std::convert::From] for enum from repr.

Where to use:

• Managing Type
• Easy to understand constants

Note:

• require #[repr(u8)] or #[repr(u16)] or …
• default is require explicit
• #[enum_repr(default)] is special attribute on variant

Enum Attribute:

• serde: automatically implements [serde::Serialize] and [serde::Deserialize]
• implicit: make it less explicit

Variant Attribute:

• default: Sets the fallback value if none of the others apply. this attribute is required to be used only once or not at all if this attribute is not used, it will be impl [std::convert::TryFrom] used, it will be impl [std::convert::From]

Examples

Normal

use more_convert::EnumRepr;
#[derive(EnumRepr, Clone, Copy, Debug, PartialEq)]
#[repr(u8)]
pub enum Test {
    Zero = 0,
    Three = 3,
    Four = 4,
}

assert_eq!(0u8, Test::Zero.into());
assert_eq!(3u8, Test::Three.into());
assert_eq!(4u8, Test::Four.into());

assert_eq!(0u8.try_into(), Ok(Test::Zero));
assert_eq!(3u8.try_into(), Ok(Test::Three));
assert_eq!(4u8.try_into(), Ok(Test::Four));

assert_eq!(TryInto::<Test>::try_into(1u8).unwrap_err(), String::from("invalid Test: 1"));

serde

use more_convert::EnumRepr;
#[derive(EnumRepr, Clone, Copy, Debug, PartialEq)]
#[repr(u8)]
#[enum_repr(serde)]
pub enum Test {
    Zero = 0,
    Three = 3,
    Four = 4,
}


assert_eq!(serde_json::to_string(&Test::Zero).unwrap(), "0");
assert_eq!(serde_json::to_string(&Test::Three).unwrap(), "3");
assert_eq!(serde_json::to_string(&Test::Four).unwrap(), "4");

assert_eq!(serde_json::from_str::<Test>("0").unwrap(), Test::Zero);
assert_eq!(serde_json::from_str::<Test>("3").unwrap(), Test::Three);
assert_eq!(serde_json::from_str::<Test>("4").unwrap(), Test::Four);

assert_eq!(serde_json::from_str::<Test>("1").unwrap_err().to_string(), String::from("invalid Test: 1"));

implicit

use more_convert::EnumRepr;
#[derive(EnumRepr, Clone, Copy, Debug, PartialEq)]
#[repr(u8)]
#[enum_repr(implicit)]
pub enum Test {
    Zero,
    Three = 3,
    Four,
}

assert_eq!(0u8, Test::Zero.into());
assert_eq!(3u8, Test::Three.into());
assert_eq!(4u8, Test::Four.into());

assert_eq!(0u8.try_into(), Ok(Test::Zero));
assert_eq!(3u8.try_into(), Ok(Test::Three));
assert_eq!(4u8.try_into(), Ok(Test::Four));

assert_eq!(TryInto::<Test>::try_into(1u8).unwrap_err(), String::from("invalid Test: 1"));

default

use more_convert::EnumRepr;
#[derive(EnumRepr, Clone, Copy, Debug, PartialEq)]
#[repr(u8)]
pub enum Test {
    Zero = 0,
    One = 1,
    #[enum_repr(default)]
    Two = 2,
}

assert_eq!(0u8, Test::Zero.into());
assert_eq!(1u8, Test::One.into());
assert_eq!(2u8, Test::Two.into());

// Invalid values return the default variant
assert_eq!(Test::Two, 255u8.into());