Update code example

Author: Bastian Gruber

ch_03/src/main.rs

@@ -52,17 +52,17 @@ impl Reject for InvalidId {}
 
 async fn get_questions() -> Result<impl warp::Reply, warp::Rejection> {
     let question = Question::new(
-        QuestionId::from_str("1").expect("No id provided"),
+        QuestionId::from_str("A").expect("No id provided"),
         "First Question".to_string(),
         "Content of question".to_string(),
         Some(vec!("faq".to_string())),
     );        
 
-        match question.id.0.is_empty() {
-            true =>  {
+        match question.id.0.parse::<i32>() {
+            Err(_) =>  {
                 Err(warp::reject::custom(InvalidId))
             },
-            false => {
+            Ok(_) => {
                 Ok(warp::reply::json(
                     &question
                 ))