Function tweetr::util::prompt_nonzero_len

pub fn prompt_nonzero_len<R, W, F>(
    input: &mut R, 
    output: &mut W, 
    prompt_s: &str, 
    verifier: F
) -> IoResult<String> where
    R: BufRead,
    W: Write,
    F: Fn(&String) -> bool, 

Ask the user to input a string of non-zero length, (re)prompting as necessary.

Examples

Allow anything as long as it's something:

assert_eq!(prompt_nonzero_len(&mut Cursor::new(b"123456789"),
                              &mut Vec::new(),
                              "Allowed chars",
                              |_| true).unwrap(),
           "123456789".to_string());

Allow valid u64s:

assert_eq!(prompt_nonzero_len(&mut Cursor::new(b"123456789"),
                              &mut Vec::new(),
                              "Number",
                              |s| u64::from_str(s).is_ok()).unwrap(),
           "123456789".to_string());
assert!(prompt_nonzero_len(&mut Cursor::new(b"123abcdef"),
                           &mut Vec::new(),
                           "Number",
                           |s| u64::from_str(s).is_ok()).is_err());