Replacing a borrowed variable [duplicate]

Answer 1

I agree with David Grayson, there's no obvious need to recreate the RwLock. Assuming you need the vector after filling it up, use mem::replace to switch out the Vec:

use std::sync::RwLock;
use std::mem;

fn main() {
    let locked = RwLock::new(Vec::::new());
    let mut writer = locked.write().unwrap();    

    for v in 0..100 {
        if writer.len() > 4 {
            let old_vec = mem::replace(&mut *writer, Vec::new());
        }
        writer.push(v);
    }
}

If you don't need the Vec, then just call Vec::clear.