Global mutable variables in Rust

help
4

Hey, we use Tauri for an application at work!

You should use Builder::manage() to tell Tauri to manage a piece of state and make it accessible to your commands later on. All you'll need to do is add a universe: tauri::State<Universe> argument to your command function.

I'll copy the example here:

use std::{collections::HashMap, sync::Mutex};
use tauri::State;
// here we use Mutex to achieve interior mutability
struct Storage {
  store: Mutex<HashMap<u64, String>>,
}
struct Connection;
struct DbConnection {
  db: Mutex<Option<Connection>>,
}

#[tauri::command]
fn connect(connection: State<DbConnection>) {
  // initialize the connection, mutating the state with interior mutability
  *connection.db.lock().unwrap() = Some(Connection {});
}

#[tauri::command]
fn storage_insert(key: u64, value: String, storage: State<Storage>) {
  // mutate the storage behind the Mutex
  storage.store.lock().unwrap().insert(key, value);
}

tauri::Builder::default()
  .manage(Storage { store: Default::default() })
  .manage(DbConnection { db: Default::default() })
  .invoke_handler(tauri::generate_handler![connect, storage_insert])
  // on an actual app, remove the string argument
  .run(tauri::generate_context!("test/fixture/src-tauri/tauri.conf.json"))
  .expect("error while running tauri application");

Global variables really hurt you in the long run because it makes it hard to manage access to the state, and their singleton nature makes testing quite difficult.

6 Likes