tvl-depot/examples/undefer.rs
2017-10-22 17:35:45 +02:00

40 lines
819 B
Rust

// Go's defer in Rust, with a little twist!
struct Defer<F: Fn()> {
f: F
}
impl <F: Fn()> Drop for Defer<F> {
fn drop(&mut self) {
(self.f)()
}
}
// Only added this for Go-syntax familiarity ;-)
fn defer<F: Fn()>(f: F) -> Defer<F> {
Defer { f }
}
// Changed your mind about the defer?
// (Note: This leaks the closure! Don't actually do this!)
fn undefer<F: Fn()>(token: Defer<F>) {
use std::mem;
mem::forget(token);
}
fn main() {
let mut i = 1;
// Calling it "token" ... could be something else. The lifetime of this
// controls when the action is run.
let token = defer(move || println!("Value is: {}", i));
i += 1;
println!("Value is: {}", i);
// Oh, now I changed my mind about the previous defer:
undefer(token);
}
// Prints:
// Value is: 2