Env Enums

Environment-related enums

หัวข้อหลัก: VarError Enum

VarError ใช้สำหรับ error จากการอ่าน environment variables

Variants และการใช้งาน

use std::env::{self, VarError};

fn main() {
    println!("=== VarError Variants ===\n");

    // NotPresent - variable doesn't exist
    match env::var("DEFINITELY_NOT_SET_XYZ") {
        Err(VarError::NotPresent) => {
            println!("NotPresent: Variable not found");
        }
        _ => unreachable!(),
    }

    // NotUnicode - value isn't valid UTF-8
    println!("\nNotUnicode: Value contains invalid UTF-8");

    // Match on VarError
    fn get_config(key: &str) -> Result<String, String> {
        env::var(key).map_err(|e| {
            match e {
                VarError::NotPresent => {
                    format!("{} is not set", key)
                }
                VarError::NotUnicode(os_str) => {
                    format!("{} contains invalid UTF-8: {:?}", key, os_str)
                }
            }
        })
    }

    println!("\n=== Error Messages ===");
    match get_config("HOME") {
        Ok(val) => println!("HOME: {}", val),
        Err(e) => println!("Error: {}", e),
    }

    match get_config("NOT_FOUND") {
        Ok(val) => println!("Value: {}", val),
        Err(e) => println!("Error: {}", e),
    }
}