Struct Flag 

pub struct Flag {
    pub name: String,
    pub short: Option<char>,
    pub description: String,
    pub required: bool,
    pub takes_value: bool,
    pub default: Option<String>,
    pub choices: Option<Vec<String>>,
    pub repeatable: bool,
    pub env: Option<String>,
}

A named flag accepted by a command, e.g. --verbose or -v.

Flags can be boolean (no value) or value-taking (--output json). Boolean flags are stored as "true" in crate::ParsedCommand::flags when present. Use Flag::builder to construct instances.

Examples

let flag = Flag::builder("verbose")
    .short('v')
    .description("Enable verbose output")
    .build()
    .unwrap();

assert_eq!(flag.name, "verbose");
assert_eq!(flag.short, Some('v'));
assert!(!flag.takes_value);

Fields

name: String

The long flag name, used as --name on the command line and as the key in crate::ParsedCommand::flags.

short: Option<char>

Optional single-character short form, used as -c on the command line.

description: String

Human-readable description shown in help output.

required: bool

Whether the parser returns an error when this flag is absent.

takes_value: bool

Whether the flag consumes the following token (or =value) as its value.

When false the flag is boolean: its presence sets the value to "true".

default: Option<String>

Value substituted when the flag is not provided (optional flags only).

choices: Option<Vec<String>>

If set, the flag value must be one of these strings (case-sensitive). Only meaningful when takes_value is true.

repeatable: bool

If true, this flag may appear multiple times in an invocation.

For boolean flags: occurrences are counted; stored as a numeric string (e.g., -v -v -v → "3"). For value-taking flags: values are collected into a JSON array string (e.g., --tag a --tag b → ["a","b"]).

env: Option<String>

Environment variable to check when the flag is absent from the command line.

Lookup order: CLI argv → env var → default → required error.

Implementations

impl Flag

pub fn builder(name: impl Into<String>) -> FlagBuilder

Create a new FlagBuilder with the given long flag name.

Arguments

• name — The long flag name (without the -- prefix). Must be non-empty after trimming (enforced by FlagBuilder::build).

Examples

let flag = Flag::builder("dry-run").build().unwrap();
assert_eq!(flag.name, "dry-run");

Trait Implementations

impl Clone for Flag

fn clone(&self) -> Flag

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Flag

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Flag

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Hash for Flag

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 Ord for Flag

fn cmp(&self, other: &Flag) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for Flag

fn eq(&self, other: &Flag) -> 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 PartialOrd for Flag

fn partial_cmp(&self, other: &Flag) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Serialize for Flag

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Eq for Flag

impl StructuralPartialEq for Flag