Struct Arg 

pub struct Arg { /* private fields */ }

Command-line argument specification

Defines a flag or option with optional short/long forms. Can be boolean (flag) or value-taking (option).

Implementations

impl Arg

pub fn new(name: impl Into<String>) -> Self

pub fn long(self, long: impl Into<String>) -> Self

pub fn short(self, short: char) -> Self

pub fn help(self, help: impl Into<String>) -> Self

pub fn takes_value(self, takes: bool) -> Self

pub fn required(self, req: bool) -> Self

pub fn default_value(self, value: impl Into<String>) -> Self

Set a default value for the argument

Example

Arg::new("port")
    .takes_value(true)
    .default_value("8080");

pub fn possible_values(self, values: &[&str]) -> Self

Restrict possible values

Example

Arg::new("format")
    .takes_value(true)
    .possible_values(&["json", "yaml", "toml"]);

pub fn validator(self, f: Validator) -> Self

Add a custom validator function

Example

Arg::new("port")
    .takes_value(true)
    .validator(|v| {
        v.parse::<u16>()
            .map(|_| ())
            .map_err(|_| "must be a valid port number".to_string())
    });