error_handling.rs

// youtube.com/watch?v=wM6o70NAWUI

fn read_file(fnm: &str) -> Result<String, io::Error> {
    let mut s = String::new();
    File::open(fnm)?.read_to_string(&mut s)?;
    return Ok(s);
}

fn read_file_longer_version(fnm: &str) -> Result<String, io::Error> {
    let f = File::open(fnm);
    let mut f = match f {        
        Ok(fl) => fl,
        Err(e) => return Err(e)
    };
    let mut s = String::new();
    match f.read_to_string(&mut s) {
        Ok(_) => Ok(s.to_string()),
        Err(e) => Err(e)
    }
}

fn main() {
    let filename = "test.txt";

    // safe
    let res2 = read_file(filename);
    match res2 {
        Ok(data) => {
           println!("Result: {}", data);
        },
        Err(err) => {
            println!("Error: {} ", err);
        }
    }
    
    // unsafe
    let res1 = read_file(filename).unwrap();
    println!("Result: {}", res1);
}