Second portion of to-do cli in Rust

main.rs

use std::collections::HashMap;
use std::io::Read;
use std::str::FromStr;

fn main() {
    let action = std::env::args().nth(1).expect("Please specify an action");
    let item = std::env::args().nth(2).expect("Please specify an item");

    let mut todo = Todo::new().expect("Initialisation of db failed");

    if action == "add" {
        todo.insert(item);
        match todo.save() {
            Ok(_) => println!("todo saved"),
            Err(why) => println!("An error occurred: {}", why),
        }
    };
}

struct Todo {
    // use rust built in HashMap to store key - val pairs
    map: HashMap<String, bool>,
}

impl Todo {
    fn new() -> Result<Todo, std::io::Error> {
        let mut f = std::fs::OpenOptions::new()
            .write(true)
            .create(true)
            .read(true)
            .open("db.txt")?;
        let mut content = String::new();
        f.read_to_string(&mut content)?;
        let map: HashMap<String, bool> = content
            .lines()
            .map(|line| line.splitn(2, '\t').collect::<Vec<&str>>())
            .map(|v| (v[0], v[1]))
            .map(|(k, v)| (String::from(k), bool::from_str(v).unwrap()))
            .collect();
        Ok(Todo { map })
    }

    fn insert(&mut self, key: String) {
        // insert a new item into our map.
        // we pass true as value.
        self.map.insert(key, true);
    }

    fn save(self) -> Result<(), std::io::Error> {
        let mut content = String::new();
        for (k, v) in self.map {
            let record = format!("{}\t{}\n", k, v);
            content.push_str(&record)
        }
        std::fs::write("db.txt", content)
    }
}

When I run cargo run -- add "make coffee", it had created a db,txt in root path, then I cannot run cargo run --add "make pancakes".

the terminus had error like this:

cargo run -- add "make pancakes"
    Finished dev [unoptimized + debuginfo] target(s) in 0.00s
     Running `target\debug\rodo.exe add "make pancakes"`
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: ParseBoolError', src\main.rs:44:63
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
error: process didn't exit successfully: `target\debug\rodo.exe add "make pancakes"` (exit code: 101)

I find this error in this code ,I code let record = format!("{}\t{}\n", k, v); into let record = format!("{}\t {}\n", k, v);, then I had this Bug, could you tell me why?

for (k, v) in self.map {
            let record = format!("{}\t{}\n", k, v);
            content.push_str(&record);
        }

Hi @iA10N3, is this the command you are running?
cargo run --add "make pancakes".

If so that is not correct. When running a binary with cargo run, the arguments are passed into the binary after two dashes. See here for more detials.

So the correct command should be: cargo run -- add "make pancakes"
Notice the space between -- and add.

Hope this helps.

Thank you very much.