Shared via Rust Playground

playground.rs

use std::collections::HashMap;

struct User {
    reference: String,
    email: String
}

fn main() {

    let mut users: HashMap<String, User> = HashMap::new();
    users.insert("first".to_string(), User { reference: "ref1".to_string(), email: "test@test.com".to_string() });
    users.insert("second".to_string(), User { reference: "ref2".to_string(), email: "test1@test.com".to_string() });
    users.insert("third".to_string(), User { reference: "ref3".to_string(), email: "test3@test.com".to_string() });

    //this is my failed attempt
    let user_refs: Vec<String> = users.iter().map(|(_, user)| user.reference.clone()).collect();

}