Trait go_flag::FlagValue

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

    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.

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Provided methods

fn is_bool_flag() -> bool

Indicates whether the flag is a boolean flag.

For most types, this is false.

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Implementations on Foreign Types

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>

impl FlagValue for String

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

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>

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Implementors

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