clap/examples/tutorial_derive/03_01_flag_count.rs

use clap::Parser;

#[derive(Parser)]
#[clap(author, version, about, long_about = None)]
struct Cli {
    #[clap(short, long, action = clap::ArgAction::Count)]
    verbose: u8,
}

fn main() {
    let cli = Cli::parse();

    println!("verbose: {:?}", cli.verbose);
}
docs: Re-work examples This creates distinct tutorial examples from complex feature examples (more how-tos). Both sets are getting builder / derive versions (at least the critical ones). 2021-11-30 18:30:19 +00:00			`use clap::Parser;`

			`#[derive(Parser)]`
docs(examples): Steer people to know about about vs long_about `#[clap(about)]` only overrides `about`. If the doc comment also sets `long_about`, it won't be overridden. This change is to help raise visibility of reseting `long_about` in these cases. 2022-01-11 00:47:20 +00:00			`#[clap(author, version, about, long_about = None)]`
docs: Re-work examples This creates distinct tutorial examples from complex feature examples (more how-tos). Both sets are getting builder / derive versions (at least the critical ones). 2021-11-30 18:30:19 +00:00			`struct Cli {`
feat(derive): Expose control over Actions This is the derive support for #3774 (see also #3775, #3777) This combined with `value_parser` replaces `parser`. The main frustration with this is that `ArgAction::Count` (the replacement for `parse(from_occurrences)` must be a `u64`. We could come up with a magic attribute that is meant to be the value parser's parsed type. We could then use `TryFrom` to convert the parsed type to the user's type to allow more. That is an exercise for the future. Alternatively, we have #3792. Prep for this included - #3782 - #3783 - #3786 - #3789 - #3793 2022-06-01 15:31:23 +00:00			`#[clap(short, long, action = clap::ArgAction::Count)]`
perf(parser): Take up less memory with ArgAction::Count Someone should not reasonably expect a coun flag to go up to billions, millions, or even thousands. 255 should be sufficient for anyone, right? The original type was selected to be consistent with `ArgMatches::occurrences_of` but that is also used for tracking how many values appear which can be large with `xargs`. I'm still conflicted on what the "right type" is an wish we could support any numeric type. When I did a search on github though, every case was for debug/quiet flags and only supported 2-3 occurrences, making a `u8` overkill. This came out of a discussion on #3792 2022-06-09 16:09:36 +00:00			`verbose: u8,`
docs: Re-work examples This creates distinct tutorial examples from complex feature examples (more how-tos). Both sets are getting builder / derive versions (at least the critical ones). 2021-11-30 18:30:19 +00:00			`}`

			`fn main() {`
			`let cli = Cli::parse();`

			`println!("verbose: {:?}", cli.verbose);`
			`}`