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//! How to parse `--foo=true --bar=false` and turn them into bool.
use structopt::StructOpt;
fn true_or_false(s: &str) -> Result<bool, &'static str> {
match s {
"true" => Ok(true),
"false" => Ok(false),
_ => Err("expected `true` or `false`"),
}
}
#[derive(StructOpt, Debug, PartialEq)]
struct Opt {
// Default parser for `try_from_str` is FromStr::from_str.
// `impl FromStr for bool` parses `true` or `false` so this
// works as expected.
#[structopt(long, parse(try_from_str))]
foo: bool,
// Of course, this could be done with an explicit parser function.
#[structopt(long, parse(try_from_str = true_or_false))]
bar: bool,
// `bool` can be positional only with explicit `parse(...)` annotation
#[structopt(long, parse(try_from_str))]
boom: bool,
}
fn main() {
assert_eq!(
Opt::from_iter(&["test", "--foo=true", "--bar=false", "true"]),
Opt {
foo: true,
bar: false,
boom: true
}
);
// no beauty, only truth and falseness
assert!(Opt::from_iter_safe(&["test", "--foo=beauty"]).is_err());
}
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