Step 5: Page 30

src/main.rs

@@ -49,6 +49,12 @@ impl TodoList {
             Ok(TodoList::new())
         }
     }
+
+    fn save_to_file(&self, filename: &str) -> Result<(), Box<dyn std::error::Error>> {
+        let json = serde_json::to_string_pretty(self)?;
+        fs::write(filename, json)?;
+        Ok(())
+    }
 }
 fn main() {
     let cli = Cli::parse();