How can I create a vector of structs in a loop

I’m trying to learn Rust and am using the advent of code to do so. I’ve just started and have decided to have a vector containing "Elf" structs, of which each will contain a vector calory_items.

I’m trying to create this from a text file and have the following code:

use std::io::{self, BufReader};
use std::path::Path;
use std::io::prelude::*;
use std::fs::File;

struct Elf {
    calory_items: Vec<i32>
}

fn parse_meal_list(source: &str) -> Vec<Elf> {
    let file = File::open(source).unwrap();
    let file = BufReader::new(file);
    
    let mut elves: Vec<Elf> = Vec::new();
    let mut elf = Elf {
        calory_items: Vec::new()
    };

    for line in file.lines() {
        let line = line.unwrap();
        if line.is_empty() {
            // create new Elf
            if elf.calory_items.len() > 0 {
                // in case there are two empty lines
                elves.push(elf);
                let mut elf: Elf = Elf { calory_items: Vec::new() };
            }
        } else {
            // append to current Elf object the calories
            let calory_item: i32 = line.parse().unwrap();
            elf.calory_items.push(calory_item)
        }
    }
    return elves;
}


fn main() {
    let input_day_1_source = Path::new("input_files/day_1.txt");
    let input_day_1_source = input_day_1_source.to_str().unwrap();
    let Elves: Vec<Elf> = parse_meal_list(input_day_1_source);
}

The compiler gives me the following error:

error[E0382]: borrow of moved value: `elf`
  --> src/main.rs:23:16
   |
15 |     let mut elf = Elf {
   |         ------- move occurs because `elf` has type `Elf`, which does not implement the `Copy` trait
...
19 |     for line in file.lines() {
   |     ------------------------ inside of this loop
...
23 |             if elf.calory_items.len() > 0 {
   |                ^^^^^^^^^^^^^^^^^^^^^^ value borrowed here after move
24 |                 // in case there are two empty lines
25 |                 elves.push(elf);
   |                            --- value moved here, in previous iteration of loop

I read the Rust book about the borrow checker but don’t know how I can append an item to the list and return the ownership (or solve it another way).

>Solution :

I assume that with:

let mut elf: Elf = Elf { calory_items: Vec::new() };

You intended to initialize elf with an empty Elf again. But this does not do what you want. Instead, it creates a separate variable that shadows elf, making it inaccessible for the rest of the block but does not change the original elf variable. You need to use assignment:

elf = Elf { calory_items: Vec::new() };