Rust console loading percentage for iterator

loader.rs

use std::io::{self, prelude::*};
use std::thread;
use std::time::Duration;

struct Loader<I> {
    iter: I,
    len: usize,
    progress: usize,
}

impl<I: ExactSizeIterator> Loader<I> {
    fn new(iter: I) -> Self {
        Loader {
            len: iter.len(),
            iter,
            progress: 0,
        }
    }

    fn run(mut self) -> io::Result<()> {
        while self.iter.next().is_some() {
            self.progress += 1;
            print!("\rLoading... {:.0}%", (self.progress as f32 / self.len as f32) * 100.0);
            io::stdout().flush()?;
        }
        println!("\rLoading... Done.");
        Ok(())
    }
}

fn loading() -> io::Result<()> {
    let items: Vec<_> = (0..100).collect();
    let time_per_item = (2000 / items.len()) as u64;
    Loader::new(items.iter().map(|item| {
        thread::sleep(Duration::from_millis(time_per_item));
        item
    })).run()
}

fn main() {
    if let Err(e) = loading() {
        eprintln!("Error: {:?}", e);
    }
}