anyhow_match.rs

anyhow_match.rs

use anyhow::Result;

// The same function as before that might fail.
fn get_user_id(username: &str) -> Result<u32> {
    if username.is_empty() {
        anyhow::bail!("Username cannot be empty");
    }
    Ok(42)
}

// The 'main' function returns 'Result<()>' so it can still use 'anyhow'.
fn main() -> Result<()> {
    // Call the function with an invalid (empty) username.
    let result = get_user_id("");

    // Use a 'match' expression to handle the 'Result' explicitly.
    match result {
        // If the result is 'Ok', we can access the value.
        Ok(user_id) => {
            println!("Successfully retrieved user ID: {}", user_id);
        }
        // If the result is 'Err', we can access the 'anyhow::Error'.
        Err(e) => {
            // 'e' is a reference to the error, and we can print it.
            eprintln!("Error occurred: {:?}", e);
            // You can also get more details, such as the backtrace.
            // eprintln!("Error with backtrace: {:?}", e.backtrace());
        }
    }

    // This line will now be reached because we handled the error with 'match'
    // instead of propagating it with '?'.
    println!("Program finished.");

    // The function still needs to return an 'Ok' result if everything
    // concludes without a propagated error.
    Ok(())
}