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// In the following example we will create an enum with 4 values, assign a positional argument
// that accepts only one of those values, and use clap to parse the argument.
//
// Start with bringing the trait into scope.
use std::str::FromStr;
// Add clap like normal
#[macro_use]
extern crate clap;
use clap::{App, Arg};
// Define your enum
enum Vals {
Foo,
Bar,
Baz,
Qux
}
// Implement the trait
impl FromStr for Vals {
type Err = &'static str;
fn from_str(s: &str) -> Result<Self, Self::Err> {
match s {
"Foo" => Ok(Vals::Foo),
"Bar" => Ok(Vals::Bar),
"Baz" => Ok(Vals::Baz),
"Qux" => Ok(Vals::Qux),
_ => Err("no match")
}
}
}
fn main() {
// Create the application like normal
let m = App::new("myapp")
// Use a single positional argument that is required
.arg(Arg::from_usage("<type> 'The type to use'")
// Define the list of possible values
.possible_values(&["Foo", "Bar", "Baz", "Qux"]))
.get_matches();
let t = value_t!(m, "type", Vals).unwrap_or_else(|e| e.exit());
// Now we can use our enum like normal.
match t {
Vals::Foo => println!("Found a Foo"),
Vals::Bar => println!("Found a Bar"),
Vals::Baz => println!("Found a Baz"),
Vals::Qux => println!("Found a Qux")
}
}
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