Tipos de Errores Dinámicos
Sometimes we want to allow any type of error to be returned without writing our own enum covering all the different possibilities. The std::error::Error trait makes it easy to create a trait object that can contain any error.
use std::error::Error;
use std::fs;
use std::io::Read;
fn read_count(path: &str) -> Result<i32, Box<dyn Error>> {
let mut count_str = String::new();
fs::File::open(path)?.read_to_string(&mut count_str)?;
let count: i32 = count_str.parse()?;
Ok(count)
}
fn main() {
fs::write("count.dat", "1i3").unwrap();
match read_count("count.dat") {
Ok(count) => println!("Recuento: {count}"),
Err(err) => println!("Error: {err}"),
}
}La función read_count puede devolver std::io::Error (de las operaciones de archivos) o std::num::ParseIntError (de String::parse).
Boxing errors saves on code, but gives up the ability to cleanly handle different error cases differently in the program. As such it’s generally not a good idea to use Box<dyn Error> in the public API of a library, but it can be a good option in a program where you just want to display the error message somewhere.
Asegúrate de implementar el trait std::error::Error al definir un tipo de error personalizado para que pueda tener una estructura box. Sin embargo, si necesitas el atributo no_std, ten en cuenta que el trait std::error::Error de momento solo es compatible con no_std en nightly.