EnumIndex

EnumIndex is a trait to extract variant index from enums in Rust. IndexEnum is a trait that allows you to get an enum variant by indexing. It only works if all parameters of Enum implement Default

The main case is implementation of your own enum serialization.

pub trait EnumIndex {
    fn enum_index(&self) -> usize;
}

pub trait IndexEnum {
    fn index_enum(index: usize) -> Option<Self> where Self: Sized;
}

Example

extern crate enum_index;
#[macro_use]
extern crate enum_index_derive;
#[macro_use]
extern crate index_enum_derive;
use enum_index::{EnumIndex, IndexEnum};

#[derive(EnumIndex)]
enum Object {
    None,                    // 0
    Number(u64),             // 1
    Point {x: f32, y: f32}   // 2
}

// IndexEnum can only be derived for C-like enums
#[derive(EnumIndex, IndexEnum, Debug)]
enum OpCode {
    Disconnect,                       // 0
    SendData(String),                 // 1
    SomethingElse { a: f32, b: u64 }  // 2
}

fn main() {
    let first = Object::None;
    let second = Object::Number(0u64);
    let third = Object::Point {x: 0f32, y: 0f32};
    println!("{}", first.enum_index()); // prints 0
    println!("{}", second.enum_index()); // prints 1
    println!("{}", third.enum_index()); // prints 2

    let send_data_variant = OpCode::index_enum(2).unwrap();
    println!("{:?}", send_data_variant); // prints SomethingElse{a: 0f32, b: 0u64}
}

Using in your project

Add the following in your Cargo.toml file

[dependencies]
enum_index = "*"
enum_index_derive = "*"

Then import needed trait and macro

// Strum contains all the trait definitions
extern crate enum_index;
#[macro_use]
extern crate enum_index_derive;