[−][src]Trait parse_arg::ParseArg

pub trait ParseArg: Sized {
    type Error: Display;
    fn parse_arg(arg: &OsStr) -> Result<Self, Self::Error>;
    fn describe_type<W: Write>(writer: W) -> Result;

    fn parse_owned_arg(arg: OsString) -> Result<Self, Self::Error> { ... }
}

Defines an interface for types that can be created by parsing command-line argument.

This trait is similar to FromStr. See the crate documentation for list of importatn differences.

Associated Types

`type Error: Display`

Type returned in Err variant of Result when parsing fails.

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Required methods

`fn parse_arg(arg: &OsStr) -> Result<Self, Self::Error>`

Parses the argument.

`fn describe_type<W: Write>(writer: W) -> Result`

Writes human-readable description of the type to the writer.

The description should be in English composed in such way that appending it to string "The input must be " sounds natural. E.g. if the description is "a number", the resulting phrase will be "The input must be a number".

This way, it can be used as a documentation/hint for the user.

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Provided methods

`fn parse_owned_arg(arg: OsString) -> Result<Self, Self::Error>`

Parses the argument consuming it.

Implementors are encouraged to specialize this method if the resulting implementation is more performant - e.g. if it avoids allocation.

The users are encouraged to use this method instead of parse_arg if they own the string and will not need it after call to this function. (Typical when working with std::env::args_os().)

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