Function dispose::defer

pub fn defer<F: FnOnce()>(f: F) -> Disposable<F>

Defer an action until the end of a lexical scope.

This function returns a value that calls the provided closure when dropped, resulting in functionality akin to try...finally blocks or Swift’s defer blocks and Go’s defer func.

Examples

use dispose::defer;

{
    let _d = defer(|| println!("Hello from defer()!"));

    println!("Hello, world!");
}
// This prints the following:
// Hello, world!
// Hello from defer()!

A more pertinent example would be the use of defer with the ? operator:

use dispose::defer;

fn tryme() -> Result<(), ()> {
    let _d = defer(|| println!("Cleaning up..."));

    println!("Hello!");

    let uh_oh = Err(())?; // Pretend this was a function that failed

    println!("You can't see me: {:?}", uh_oh);

    Ok(())
}

println!("hi");

tryme().map_err(|()| println!("ERROR: Something went wrong.")).unwrap_err()

// This prints the following:
// Hello!
// Cleaning up...
// ERROR: Something went wrong.