#Rust πŸ¦€ – Accesing external vars in threads πŸ§΅

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:

  • A main thread where we declare a string var with a message.
  • The 2nd thread that will display a message using the main thread message.
/*
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();
}

The code output shows that the app is closed before finishing the execution of the 2nd thread.

Run outuput with the message from the 2nd thread using a var from the main thread

Super cool !

Happy coding!

Greetings

El Bruno

More posts in my blog ElBruno.com.


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