In Rust, is there a way to iterate through the values of an enum?

Question

I come from a Java background and I might have something like enum Direction { NORTH, SOUTH, EAST, WEST} and I could do something with each of the values in turn with the enhanced for loop like:

for(Direction dir : Direction.values())  {     //do something with dir } 

I would like to do a similar thing with Rust enums.

Answer 1

You can use the strum crate to easily iterate through the values of an enum.

use strum::IntoEnumIterator; // 0.17.1 use strum_macros::EnumIter; // 0.17.1  #[derive(Debug, EnumIter)] enum Direction {     NORTH,     SOUTH,     EAST,     WEST, }  fn main() {     for direction in Direction::iter() {         println!("{:?}", direction);     } } 

Output:

NORTH SOUTH EAST WEST 

Answer 2

If the enum is C-like (as in your example), then you can create a static array of each of the variants and return an iterator of references to them:

use self::Direction::*; use std::slice::Iter;  #[derive(Debug)] pub enum Direction {     North,     South,     East,     West, }  impl Direction {     pub fn iterator() -> Iter<'static, Direction> {         static DIRECTIONS: [Direction; 4] = [North, South, East, West];         DIRECTIONS.iter()     } }  fn main() {     for dir in Direction::iterator() {         println!("{:?}", dir);     } } 

If you make the enum implement Copy, you can use Iterator::copied and return impl Trait to have an iterator of values:

impl Direction {     pub fn iterator() -> impl Iterator<Item = Direction> {         [North, South, East, West].iter().copied()     } } 

See also:

• What is the correct way to return an Iterator (or any other trait)?
• Why can I return a reference to a local literal but not a variable?