string_vs_str_short_lived_struct.rs

#![allow(dead_code)]

struct CommandArg<'o> {
  names: &'o [&'o str],
  help_text: &'o str,
}

fn parse_args_and_run_etc(args: &[CommandArg]) {
  print!("Usage: app thingy ");
  
  for arg in args {
    match arg.names.first() {
      Some(n) => print!("{} <VALUE> ", n),
      None => print!("<VALUE> "),
    }
  }
  
  println!("");
}
  
pub fn hypothetical_subcommand() {
  let path = CommandArg {
    names: &["--path", "-p"],
    help_text: "The directory in which to create the instance.",
  };
  
  let name = CommandArg { names: &[], help_text: "The name of the instance to create." };
  
  parse_args_and_run_etc(&[path, name]);
}

fn main() {
  hypothetical_subcommand();
}

Here's a version with Cow:

#![allow(dead_code)]

use std::borrow::Cow;

struct CommandArg<'o> {
  names: &'o [&'o str],
  help_text: Cow<'o, str>
}

fn parse_args_and_run_etc(args: &[CommandArg]) {
  print!("Usage: app thingy ");

  for arg in args {
    match arg.names.first() {
      Some(n) => print!("{} <VALUE> ", n),
      None => print!("<VALUE> "),
    }
  }

  println!("");

  for arg in args {
      println!("{}", arg.help_text);
  }

}

pub fn hypothetical_subcommand() {
  let path = CommandArg {
    names: &["--path", "-p"],
    help_text: Cow::Borrowed("The directory in which to create the instance."),
  };

  let name = CommandArg { names: &[], help_text: Cow::Owned("The name of the instance to create.".to_string()) };

  parse_args_and_run_etc(&[path, name]);
}

fn main() {
  hypothetical_subcommand();
}