Trait FromArgMatches

pub trait FromArgMatches: Sized {
    // Required methods
    fn from_arg_matches(matches: &ArgMatches) -> Result<Self, Error>;
    fn update_from_arg_matches(
        &mut self,
        matches: &ArgMatches,
    ) -> Result<(), Error>;

    // Provided methods
    fn from_arg_matches_mut(matches: &mut ArgMatches) -> Result<Self, Error> { ... }
    fn update_from_arg_matches_mut(
        &mut self,
        matches: &mut ArgMatches,
    ) -> Result<(), Error> { ... }
}

Converts an instance of ArgMatches to a user-defined container.

Derived as part of Parser, Args, and Subcommand.

Required Methods

fn from_arg_matches(matches: &ArgMatches) -> Result<Self, Error>

Instantiate Self from ArgMatches, parsing the arguments as needed.

Motivation: If our application had two CLI options, --name <STRING> and the flag --debug, we may create a struct as follows:

struct Context {
    name: String,
    debug: bool
}

We then need to convert the ArgMatches that clap generated into our struct. from_arg_matches serves as the equivalent of:

impl From<ArgMatches> for Context {
   fn from(m: ArgMatches) -> Self {
       Context {
           name: m.get_one::<String>("name").unwrap().clone(),
           debug: m.get_flag("debug"),
       }
   }
}

fn update_from_arg_matches(&mut self, matches: &ArgMatches) -> Result<(), Error>

Assign values from ArgMatches to self.

Provided Methods

fn from_arg_matches_mut(matches: &mut ArgMatches) -> Result<Self, Error>

Instantiate Self from ArgMatches, parsing the arguments as needed.

Motivation: If our application had two CLI options, --name <STRING> and the flag --debug, we may create a struct as follows:

struct Context {
    name: String,
    debug: bool
}

We then need to convert the ArgMatches that clap generated into our struct. from_arg_matches_mut serves as the equivalent of:

impl From<ArgMatches> for Context {
   fn from(m: ArgMatches) -> Self {
       Context {
           name: m.get_one::<String>("name").unwrap().to_string(),
           debug: m.get_flag("debug"),
       }
   }
}

fn update_from_arg_matches_mut( &mut self, matches: &mut ArgMatches, ) -> Result<(), Error>

Assign values from ArgMatches to self.

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<T> FromArgMatches for Box<T>

where T: FromArgMatches,

fn from_arg_matches(matches: &ArgMatches) -> Result<Box<T>, Error>

fn from_arg_matches_mut(matches: &mut ArgMatches) -> Result<Box<T>, Error>

fn update_from_arg_matches(&mut self, matches: &ArgMatches) -> Result<(), Error>

fn update_from_arg_matches_mut( &mut self, matches: &mut ArgMatches, ) -> Result<(), Error>

Implementors