I want to use the clap derive API in order to parse an Ipv4Addr
.
#![allow(unused)]
use clap; // 3.1.6
use clap::Parser;
use std::net::Ipv4Addr;
#[derive(Parser, Debug)]
#[clap(author, version, about, long_about = None)]
struct Args {
#[clap(short, long, parse(from_str))]
ip_dst: Ipv4Addr,
}
fn main() {
let args = Args::parse();
}
My attempt gives the following error even though Ipv4Addr seems to implement FromStr
which provides from_str
error[E0277]: the trait bound `Ipv4Addr: From<&str>` is not satisfied
--> src/main.rs:10:31
|
10 | #[clap(short, long, parse(from_str))]
| ^^^^^^^^ the trait `From<&str>` is not implemented for `Ipv4Addr`
|
= help: the following implementations were found:
<Ipv4Addr as From<[u8; 4]>>
<Ipv4Addr as From<u32>>
For more information about this error, try `rustc --explain E0277`.
My Questions are:
FromStr
used? What you want is what is used by default (since Ipv4Addr
implements FromStr
), without specifiying any parse
option:
use clap; // 3.1.6
use clap::Parser;
use std::net::Ipv4Addr;
#[derive(Parser, Debug)]
#[clap(author, version, about, long_about = None)]
struct Args {
#[clap(short, long)]
ip_dst: Ipv4Addr,
}
Otherwise, you need to use try_from_str
as per the example:
#![allow(unused)]
use clap; // 3.1.6
use clap::Parser;
use std::net::Ipv4Addr;
#[derive(Parser, Debug)]
#[clap(author, version, about, long_about = None)]
struct Args {
#[clap(short, long, parse(try_from_str))]
ip_dst: Ipv4Addr,
}
Ipv4Addr
implements FromStr
but not From<&str>
which is the From
trait with &str
as a parameter. If you want to use FromStr
, specify parse(try_from_str)
or omit it since it's the default .
Update for Clap v4
use clap::{arg, value_parser, Command}; // Clap v4
use std::net::Ipv4Addr;
fn main() {
let matches = Command::new("clap-test")
.arg(
arg!(--ip <VALUE>)
.default_value("127.0.0.1")
.value_parser(value_parser!(Ipv4Addr)),
)
.get_matches();
println!(
"IP {:?}",
matches.get_one::<Ipv4Addr>("ip").expect("required"),
);
}
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