Macros
Conversion between Enum and u32
Macro from https://stackoverflow.com/questions/28028854/how-do-i-match-enum-values-with-an-integer.
Example
use std::convert::{TryFrom, TryInto}; macro_rules! back_to_enum { {$(#[$meta:meta])* $vis:vis enum $name:ident { $($(#[$vmeta:meta])* $vname:ident $(= $val:expr)?,)* }} => { $(#[$meta])* $vis enum $name { $($(#[$vmeta])* $vname $(= $val)?,)* } impl TryFrom<u32> for $name { type Error = (); fn try_from(v: u32) -> Result<Self, Self::Error> { match v { $(x if x == $name::$vname as u32 => Ok($name::$vname),)* _ => Err(()), } } } } } back_to_enum! { #[derive(Clone, Copy, Debug)] enum Number { Zero, One, Two, } } fn main() { let i: u32 = 1; let n: Number = i.try_into().unwrap(); println!("{:?}", n); // One let i = n as i32; println!("{}", i); // 1 }
Code
use std::convert::{TryFrom, TryInto};
macro_rules! back_to_enum {
{$(#[$meta:meta])* $vis:vis enum $name:ident {
$($(#[$vmeta:meta])* $vname:ident $(= $val:expr)?,)*
}} => {
$(#[$meta])*
$vis enum $name {
$($(#[$vmeta])* $vname $(= $val)?,)*
}
impl TryFrom<u32> for $name {
type Error = ();
fn try_from(v: u32) -> Result<Self, Self::Error> {
match v {
$(x if x == $name::$vname as u32 => Ok($name::$vname),)*
_ => Err(()),
}
}
}
}
}
Last modified on 231008.