num_enum
========
Procedural macros to make inter-operation between primitives and enums easier.
This crate is no_std compatible.
[](https://crates.io/crates/num_enum)
[](https://docs.rs/num_enum)
[](https://travis-ci.org/illicitonion/num_enum)
Turning an enum into a primitive
--------------------------------
```rust
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
----------------------------------------------
```rust
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:
```rust
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.