m3tam3re.com/content/posts/rust-2.en.md

title, date, draft, series, tags

title	date	draft	series	tags
Part 2: Result Type and error handling	2020-09-19	false	Starting with rust	rust coding

Today I experimented with the subject of error handling. One of several ways in Rust is the Result type. This is an enum that either contains a value for the success case or an error.

use std::string::String;

#[derive(Debug)]
struct Person {
    name: String,
    age: i32,
}

impl Person {
    fn hello(&self) -> Result<String, &str>{
        if self.name != "" {
            let ret = format!("{} is {} years old.", self.name, self.age);
            Ok(ret)
        } else {
            Err("No name given")
        }
        
    }
}

fn main() {
    let bob = Person {
        name: String::from("Bob"),
        age: 32,
    };
    let res = bob.hello().unwrap(); // will consume the Ok value or panic in case of error
    println!("{:?}", res);
    
    let mary = Person {
        name: String::from(""),
        age: 30,
    };
    let res1 = mary.hello().unwrap(); // will consume the Ok value or panic in case of error
    println!("{:?}", res1); 
}

By appending the method unwrap() the returned Result type is unpacked. In the event of an error, unwrap() leads to panic.

The output looks like this:

Standard Error:
Compiling playground v0.0.1 (/playground)
    Finished dev [unoptimized + debuginfo] target(s) in 1.05s
     Running `target/debug/playground`
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: "No name given"', src/main.rs:33:29
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Standard Output:
"Bob is 32 years old."

I think that's just the beginning. Using the method unwrap() is quick and easy, but usually you would not want your program to quit with a panic on error.