Step 4: page 29

src/main.rs

@@ -1,5 +1,7 @@
 use clap::{Parser, Subcommand};
 use serde::{Deserialize, Serialize};
+use std::fs;
+use std::path::Path;
 
 #[derive(Parser)]
 #[command(name = "todo")]
@@ -30,6 +32,24 @@ struct TodoList {
     next_id: usize,
 }
 
+impl TodoList {
+    fn new() -> Self {
+        TodoList {
+            tasks: Vec::new(),
+            next_id: 1,
+        }
+    }
+
+    fn load_from_file(filename: &str) -> Result<Self, Box<dyn std::error::Error>> {
+        if Path::new(filename).exists() {
+            let contents = fs::read_to_string(filename)?;
+            let todo_list = serde_json::from_str(&contents)?;
+            Ok(todo_list)
+        } else {
+            Ok(TodoList::new())
+        }
+    }
+}
 fn main() {
     let cli = Cli::parse();
     match cli.command {