swap-option-result.rs

extern crate result;

use std::fmt::Debug;
use std::io::{ErrorKind, Result};
use std::path::Path;

use result::prelude::*;

fn check_path<P: AsRef<Path> + Debug>(path: P) -> Result<Option<P>> {
    println!("Processing path {:?}", path);
    Err(ErrorKind::NotFound.into())
}

fn select_path<I, P>(paths: I) -> Result<Option<P>>
where
    I: IntoIterator<Item = P>,
    P: AsRef<Path> + Debug,
{
    paths
        .into_iter()
        .map(check_path)
        .filter_map(ResultOptionExt::invert)
        .next_invert()
}

fn main() {
    select_path(&["/var", "/var/lib/"])
        .expect("...")
        .expect("...");
}