Code shared from the Rust Playground

playground.rs

struct AppData<'a> {
    name: &'a str
}

impl<'a> AppData<'a> {
    pub fn go_to_screen(&self, screen: &str) {
        println!("app {} is going to screen {}", self.name, screen);
    }
}

// mimicking Gtk; F: Fn() + 'static
fn button_connect_clicked<F: Fn()+'static>(closure: F) {
    closure();    
}

fn main() {
    // In my real app, AppData contains connection to database. 
    // So cannot be cloned.
    let app_data:AppData = AppData{name:"demo_app"};
    
    let app_data_ref = &app_data;
    let closure_a = || {
        app_data_ref.go_to_screen("screen1");
    };
    //gtk::init();
    //initialize window etc..
    button_connect_clicked(closure_a);
    //gtk::main();
}

/* 
Here the error is that closure_a appears to live beyond main, but app_data_ref
cease to exist after main().
Actually, we never exit the main() because call to gtk::main() blocks until app exits.
So, app_data_ref is valid as long as closure_a is valid.
What's a polite way to tell the compiler that it's wrong in this case?
*/