pub struct EnumValueParser<E: ValueEnum + Clone + Send + Sync + 'static>(_);
Expand description

Parse an ValueEnum value.

See also:

Example


#[derive(Copy, Clone, Debug, PartialEq, Eq)]
enum ColorChoice {
    Always,
    Auto,
    Never,
}

impl clap::ValueEnum for ColorChoice {
    fn value_variants<'a>() -> &'a [Self] {
        &[Self::Always, Self::Auto, Self::Never]
    }

    fn to_possible_value<'a>(&self) -> Option<clap::PossibleValue<'a>> {
        match self {
            Self::Always => Some(clap::PossibleValue::new("always")),
            Self::Auto => Some(clap::PossibleValue::new("auto")),
            Self::Never => Some(clap::PossibleValue::new("never")),
        }
    }
}

// Usage
let mut cmd = clap::Command::new("raw")
    .arg(
        clap::Arg::new("color")
            .value_parser(clap::builder::EnumValueParser::<ColorChoice>::new())
            .required(true)
    );

let m = cmd.try_get_matches_from_mut(["cmd", "always"]).unwrap();
let port: ColorChoice = *m.get_one("color")
    .expect("required");
assert_eq!(port, ColorChoice::Always);

// Semantics
let value_parser = clap::builder::EnumValueParser::<ColorChoice>::new();
// or
let value_parser = clap::value_parser!(ColorChoice);
assert!(value_parser.parse_ref(&cmd, arg, OsStr::new("random")).is_err());
assert!(value_parser.parse_ref(&cmd, arg, OsStr::new("")).is_err());
assert_eq!(value_parser.parse_ref(&cmd, arg, OsStr::new("always")).unwrap(), ColorChoice::Always);
assert_eq!(value_parser.parse_ref(&cmd, arg, OsStr::new("auto")).unwrap(), ColorChoice::Auto);
assert_eq!(value_parser.parse_ref(&cmd, arg, OsStr::new("never")).unwrap(), ColorChoice::Never);

Implementations

Parse an ValueEnum

Trait Implementations

Returns a copy of the value. Read more
Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
Returns the “default value” for a type. Read more
Argument’s value type
Parse the argument value Read more
Reflect on enumerated value properties Read more
Parse the argument value Read more
Adapt a TypedValueParser from one value to another Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The resulting type after obtaining ownership.
Creates owned data from borrowed data, usually by cloning. Read more
Uses borrowed data to replace owned data, usually by cloning. Read more
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.