# clap::value_t_or_exit! [−] [src]

    macro_rules! value_t_or_exit {
        ($m:ident, $v:expr, $t:ty) => { ... };
        ($m:ident.value_of($v:expr), $t:ty) => { ... };
    }

Convenience macro getting a typed value `T` where `T` implements `std::str::FromStr` or exiting upon error instead of returning a `Result`

NOTE: This macro is for backwards compatibility sake. Prefer `value_t!(/* ... */).unwrap_or_else(|e| e.exit())`

# Examples

    let matches = App::new("myapp")
                  .arg_from_usage("[length] 'Set the length to use as a pos whole num, i.e. 20'")
                  .get_matches();

    let len      = value_t_or_exit!(matches.value_of("length"), u32);
    let also_len = value_t_or_exit!(matches, "length", u32);

    println!("{} + 2: {}", len, len + 2);

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