E0597

Error Message

error[E0597]: `request_data` does not live long enough
  --> src/main.rs:28:22
   |
23 |         let request_data = String::from("User Request (Short Lived)");
   |             ------------ binding `request_data` declared here
...
28 |             request: &request_data,
   |                      ^^^^^^^^^^^^^ borrowed value does not live long enough
...
34 |     } // <--- 'request_data' dies here. 'ctx' dies here.
   |     - `request_data` dropped here while still borrowed
...
37 |     println!("I am still alive: {}", saved_request_ref);
   |                                      ----------------- borrow later used here

Code

struct Context<'a, 'b> {
    config: &'a str,
    request: &'b str,
}


impl<'a, 'b> Context<'a, 'b> {
    fn get_config(&self) -> &'a str {
        self.config
    }

    fn get_request(&self) -> &'b str {
        self.request
    }
}

fn main() {
    let config_data = String::from("Global Config (Long Lived)");
    let saved_config_ref;
    let saved_request_ref;

    {
	    // Issue is here! request_data dies inside this scope!
        let request_data = String::from("User Request (Short Lived)");

        // Creates the context holding both
        let ctx = Context {
            config: &config_data,
            request: &request_data,
        };

        // We extract the config reference
        saved_config_ref = ctx.get_config();
        saved_request_ref = ctx.get_request();
    } // <--- 'request_data' dies here. 'ctx' dies here.
    
    println!("I am still alive: {}", saved_config_ref);
    println!("I am still alive: {}", saved_request_ref);
}

Fix

fn main() {
    let config_data = String::from("Global Config (Long Lived)");
    let saved_config_ref;
    let saved_request_ref;
    // moved here to maintain lifetime scope
	let request_data = String::from("User Request (Short Lived)");
	
    {
        // Creates the context holding both
        let ctx = Context {
            config: &config_data,
            request: &request_data,
        };

        // We extract the config reference
        saved_config_ref = ctx.get_config();
        saved_request_ref = ctx.get_request();
    } // <--- 'request_data' dies here. 'ctx' dies here.
    
    println!("I am still alive: {}", saved_config_ref);
    println!("I am still alive: {}", saved_request_ref);
}