Enum Arg 

pub enum Arg {
    Positional {
        spec: ArgSpec,
        metadata: Metadata,
        index: usize,
        value: String,
    },
    Default {
        spec: ArgSpec,
        metadata: Metadata,
    },
    Example {
        spec: ArgSpec,
        metadata: Metadata,
    },
    None {
        spec: ArgSpec,
    },
}

A positional argument.

Variants

Positional

Fields

spec: ArgSpec

metadata: Metadata

index: usize

value: String

Default

Fields

spec: ArgSpec

metadata: Metadata

Example

Fields

spec: ArgSpec

metadata: Metadata

None

Fields

spec: ArgSpec

Implementations

impl Arg

pub fn spec(&self) -> ArgSpec

Returns the specification of this argument.

pub fn is_present(&self) -> bool

Returns true if this argument has a value.

pub fn present(self) -> Option<Self>

Returns Some(self) if this argument is present.

pub fn then<F, T, E>(self, f: F) -> Result<T, Error>

where F: FnOnce(Self) -> Result<T, E>, E: Display,

Applies additional conversion or validation to the argument.

This method allows for chaining transformations and validations when an argument is present. It first checks if the argument has a value and then applies the provided function.

Examples

let mut args = noargs::RawArgs::new(["example", "42"].iter().map(|a| a.to_string()));
let arg = noargs::arg("<NUMBER>").take(&mut args);

// Parse as number and ensure it's positive
let num = arg.then(|arg| -> Result<_, Box<dyn std::error::Error>> {
    let n: i32 = arg.value().parse()?;
    if n <= 0 {
        return Err("number must be positive".into());
    }
    Ok(n)
})?;

Errors

• Returns Error::MissingArg if self.is_present() is false (argument is missing)
• Returns Error::InvalidArg if f(self) returns Err(_) (validation or conversion failed)

pub fn present_and_then<F, T, E>(self, f: F) -> Result<Option<T>, Error>

where F: FnOnce(Self) -> Result<T, E>, E: Display,

Shorthand for self.present().map(|arg| arg.then(f)).transpose().

pub fn value(&self) -> &str

Returns the raw value of this argument, or an empty string if not present.

pub fn index(&self) -> Option<usize>

Returns the index at which the raw value of this argument was located in RawArgs.

Trait Implementations

impl Clone for Arg

fn clone(&self) -> Arg

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Arg

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Hash for Arg

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for Arg

fn eq(&self, other: &Arg) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for Arg

impl StructuralPartialEq for Arg