vendor/structopt/examples/keyvalue.rs

   1 //! How to parse "key=value" pairs with structopt.
   2
   3 use std::error::Error;
   4 use structopt::StructOpt;
   5
   6 /// Parse a single key-value pair
   7 fn parse_key_val<T, U>(s: &str) -> Result<(T, U), Box<dyn Error>>
   8 where
   9     T: std::str::FromStr,
  10     T::Err: Error + 'static,
  11     U: std::str::FromStr,
  12     U::Err: Error + 'static,
  13 {
  14     let pos = s
  15         .find('=')
  16         .ok_or_else(|| format!("invalid KEY=value: no `=` found in `{}`", s))?;
  17     Ok((s[..pos].parse()?, s[pos + 1..].parse()?))
  18 }
  19
  20 #[derive(StructOpt, Debug)]
  21 struct Opt {
  22     // number_of_values = 1 forces the user to repeat the -D option for each key-value pair:
  23     // my_program -D a=1 -D b=2
  24     // Without number_of_values = 1 you can do:
  25     // my_program -D a=1 b=2
  26     // but this makes adding an argument after the values impossible:
  27     // my_program -D a=1 -D b=2 my_input_file
  28     // becomes invalid.
  29     #[structopt(short = "D", parse(try_from_str = parse_key_val), number_of_values = 1)]
  30     defines: Vec<(String, i32)>,
  31 }
  32
  33 fn main() {
  34     let opt = Opt::from_args();
  35     println!("{:?}", opt);
  36 }