Trait FlagValue

pub trait FlagValue: Sized {
    // Required method
    fn parse(
        value: Option<&OsStr>,
        warnings: Option<&mut Vec<FlagWarning>>,
    ) -> Result<Self, FlagParseError>;

    // Provided method
    fn is_bool_flag() -> bool { ... }
}

Values that can be parsed from a string.

This is similar to FromStr, but different in the following ways:

• A source string can be None, indicating a boolean flag with no argument.
• A source string is given as &OsStr.
• The behavior is meant to be compatible with Go’s strconv by default.

Common Formats

Boolean

bool

• It can accept a boolean flag: -f instead of -f=true.
• 0, f, F, false, False, and FALSE are considered false.
• 1, t, T, true, True, and TRUE are considered true.
• Other values are treated as invalid.

Warnings:

• 0, 1, f, t, F, T, False, True, FALSE, and TRUE are considered incompatible.

Unsigned integer

u8, u16, u32, u64, u128, usize

• Sign (- or +) is not allowed.
• It may have an optional radix prefix: 0x, 0o, 0, or 0b. It’s case-insensitive.
• Unless it’s 0, it must have at least one digit, except the radix prefix.
• It may have optional underscores between the radix prefix and a digit or between digits. Underscores can’t be consecutive.

Warnings:

• radix prefixes, including 0, are considered incompatible.
  • Exception: values from 0 to 7 are unambiguous, so considered compatible.
• underscores are considered incompatible.

Signed integer

i8, i16, i32, i64, i128, isize

• Sign (- or +) is allowed at the beginning of the string.
• Otherwise same as unsigned integers.

Warnings:

• radix prefixes, including 0, are considered incompatible.
  • Exception: values from -7 to 7 are unambiguous, so considered compatible.
• underscores are considered incompatible.

Floating point number

f32, f64

Not yet implemented

UTF-8 String

String

• Any UTF-8 strings are allowed on unix-like platforms.
• Any UTF-16 strings are allowed on Windows.

No warning is defined.

OS-defined String

OsString, PathBuf

• Anything is allowed.

No warning is defined.

Required Methods

fn parse( value: Option<&OsStr>, warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

Parses the flag argument.

Errors

It may return Err when the value is an invalid string for the type.

Panics

It may panic if is_bool_flag() is false and value is None.

Provided Methods

fn is_bool_flag() -> bool

Indicates whether the flag is a boolean flag.

For most types, this is false.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl FlagValue for bool

fn is_bool_flag() -> bool

fn parse( value: Option<&OsStr>, warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for i8

fn parse( value: Option<&OsStr>, warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for i16

fn parse( value: Option<&OsStr>, warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for i32

fn parse( value: Option<&OsStr>, warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for i64

fn parse( value: Option<&OsStr>, warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for i128

fn parse( value: Option<&OsStr>, warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for isize

fn parse( value: Option<&OsStr>, warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for u8

fn parse( value: Option<&OsStr>, warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for u16

fn parse( value: Option<&OsStr>, warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for u32

fn parse( value: Option<&OsStr>, warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for u64

fn parse( value: Option<&OsStr>, warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for u128

fn parse( value: Option<&OsStr>, warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for usize

fn parse( value: Option<&OsStr>, warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for String

fn parse( value: Option<&OsStr>, _warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for OsString

fn parse( value: Option<&OsStr>, _warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

impl FlagValue for PathBuf

fn parse( value: Option<&OsStr>, _warnings: Option<&mut Vec<FlagWarning>>, ) -> Result<Self, FlagParseError>

Implementors