#Rust 🦀 – Accesing external vars in threads 🧵

#englishpost #multithread #rust

Hi !

In order to access external variables in a thread, we must use the move closure with the move keyword in the thread creation.

In example, these 2 lines will define and create a mutable variable and then a new thread where we can access the var.


let mut new_var = "hey!";
let handle =thread::spawn(move || {
// access to new_var here
})

And an example of the previous code will have:

	/*
	Copyright (c) 2023
	Author : Bruno Capuano
	Create Time : 2023 January
	Change Log :
	- Demos working with threads in Rust

	The MIT License (MIT)
	Permission is hereby granted, free of charge, to any person obtaining a copy
	of this software and associated documentation files (the "Software"), to deal
	in the Software without restriction, including without limitation the rights
	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	copies of the Software, and to permit persons to whom the Software is
	furnished to do so, subject to the following conditions:
	The above copyright notice and this permission notice shall be included in
	all copies or substantial portions of the Software.
	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	THE SOFTWARE.
	*/

	use std::thread;

	fn main() {

	let message = "Hello Bruno!";

	let handle = thread::spawn(move\|\| {
	println!("Message from main thread: {}", message);
	});

	handle.join().unwrap();
	}