Cannot move out of shared reference of a recursive struct - rust

Question

I am trying to implement Gale-Shapley algorithm in Rust and I need to declare a recursive struct like this:
#[derive(Eq, PartialEq, PartialOrd)]
struct Person {
name: char,
preference: Vec<Person>,
pref_index: usize,
candidates: Vec<Person>,
partner: Option<Box<Person>>, // using Box makes it easier to declare recursive structs
}
impl Person {
fn propose_to_next(&mut self) {
/* propose to next most preferred person */
if self.pref_index >= self.preference.len() {
()
}
let person = self.preference[self.pref_index];
self.candidates.push(person);
self.pref_index += 1;
}
fn pick_preferred(&mut self) {
/* pick the next more preferred partner or stay with the current one */
for person in &self.preference {
let p = Some(Box::new(*person));
if p == self.partner {
break;
} else if self.candidates.contains(&person) {
self.partner = p;
break;
}
}
}
}
But this gives me the error
error[E0507]: cannot move out of index of `std::vec::Vec<Person>`
--> src/lib.rs:18:22
|
18 | let person = self.preference[self.pref_index];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| |
| move occurs because value has type `Person`, which does not implement the `Copy` trait
| help: consider borrowing here: `&self.preference[self.pref_index]`
error[E0507]: cannot move out of `*person` which is behind a shared reference
--> src/lib.rs:29:35
|
29 | let p = Some(Box::new(*person));
| ^^^^^^^ move occurs because `*person` has type `Person`, which does not implement the `Copy` trait
How do I fix this? Is my approach flawed? I tried a non OO approach using just vectors and hashmaps but it is ugly since I will have to pass in everything in every function.

Answer 1

This should probably do it in your case.
Notice how the struct doesn't have ownership of either the elements of the preference vector or the partner but just holds a (static for simplicitly) reference to them.
Notice also that you have to implement the PartialEq trait for this to work
use std::vec::Vec;
struct Person {
name: char,
preference: Vec<&'static Person>,
partner: Option<&'static Person>
}
impl Person {
fn pick_preferred(&mut self, candidates: &Vec<Person>) {
for person in &self.preference {
if candidates.contains(&person) {
self.partner = Some(person);
}
}
}
}
impl PartialEq for Person {
fn eq(&self, other: &Self) -> bool {
self.name == other.name
}
}
pub fn main() {
let candidates: Vec<Person>;
let p: Person;
....
}
Playground link: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=4b1fab2d4f2188c8d50fd21762ad126c