Error Handling with Result and Option (page 32)

src/main.rs

@@ -77,7 +77,26 @@ impl TodoList {
         fs::write(filename, json)?;
         Ok(())
     }
+
+    fn add_task(&mut self, description: String) -> Result<(), TodoError> {
+        if description.trim().is_empty() {
+            return Err(TodoError::InvalidInput(
+                "Task description cannot be empty".to_string(),
+            ));
         }
+
+        let task = Task {
+            id: self.next_id,
+            description,
+            completed: false,
+        };
+
+        self.tasks.push(task);
+        self.next_id += 1;
+        Ok(())
+    }
+}
+
 fn main() {
     let cli = Cli::parse();
     match cli.command {