[−][src]Crate num_enum
num_enum
Procedural macros to make inter-operation between primitives and enums easier. This crate is no_std compatible.
Turning an enum into a primitive
use num_enum::IntoPrimitive; #[derive(IntoPrimitive)] #[repr(u8)] enum Number { Zero, One, } #[test] fn convert() { let zero: u8 = Number::Zero.into(); assert_eq!(zero, 0u8); }
num_enum
's IntoPrimitive
is more type-safe than using as
, because as
will silently truncate - num_enum
only derives From
for exactly the discriminant type of the enum.
Turning a primitive into an enum with try_from
use num_enum::TryFromPrimitive; use std::convert::TryInto; #[derive(Debug, Eq, PartialEq, TryFromPrimitive)] #[repr(u8)] enum Number { Zero, One, } #[test] fn convert() { let zero: Number = 0u8.try_into().unwrap(); assert_eq!(zero, Ok(Number::Zero)); let three: Result<Number, String> = 3u8.try_into(); assert_eq!(three, Err("No value in enum Number for value 3".to_owned())); }
Optional features
Some enum values may be composed of complex expressions, for example:
enum Number { Zero = (0, 1).0, One = (0, 1).1, }
To cut down on compile time, these are not supported by default, but if you enable the complex-expressions
feature of your dependency on num_enum
, these should start working.
Derive Macros
IntoPrimitive | |
TryFromPrimitive |