Rust Programming Cookbook

How to do it...

Defining error types is not hard—just follow these steps:

1. Create a new project with cargo new custom-errors and open it with VS Code.
2. Using VS Code, open src/main.rs and create a basic struct called MyError:

use std::fmt;use std::error::Error;#[derive(Debug)]pub struct MyError {    code: usize,}

3. There is an Error trait that we can implement, as follows:

impl Error for MyError {    fn description(&self) -> &str {        "Occurs when someone makes a mistake" }}

4. However, the trait also requires us (next to Debug—which we derived) to implement std::fmt::Display:

impl fmt::Display for MyError {    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {       write!(f, "Error code {:#X}", self.code)     }}

5. Lastly, let's see these traits in action ...