Function rxrust::observable::defer

pub fn defer<F, U>(observable_supplier: F) -> ObservableDeref<F> where
    F: FnOnce() -> U, 

Creates an observable that will on subscription defer to another observable that is supplied by a supplier-function which will be run once at each subscription

observable::defer(|| {
  println!("Hi!");
  observable::of("Hello!")
})
  .subscribe(move |v| {
    println!("{}", v);
  });
// Prints: Hi!\nHello!\n