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

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

Derived as part of Parser, Args, and Subcommand.

Required methods

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.value_of("name").unwrap().to_string(),
          debug: m.is_present("debug"),

Assign values from ArgMatches to self.

Implementations on Foreign Types