Hi,
I’m trying to follow the web server tutorial of 2018 rust book edition. i’m getting the following errors while trying to apply the Function boxing trick :
error[E0411]: expected trait, found self type `Self`
--> src/lib.rs:47:31
|
47 | fn call_box(self: Box<dyn Self>);
| ^^^^ `Self` is only available in traits and impls
error[E0404]: expected trait, found type parameter `F`
--> src/lib.rs:51:31
|
51 | fn call_box(self: Box<dyn F>) {
| ^ did you mean `Fn`?
for the following code :
trait FnBox {
fn call_box(self: Box<dyn Self>);
}
impl<F: FnOnce() -> ()> FnBox for F {
fn call_box(self: Box<dyn F>) {
(*self)()
}
}
Here is the complete file :
use std::sync::mpsc;
use std::sync::Arc;
use std::sync::Mutex;
use std::thread;
pub struct ThreadPool {
workers: Vec<Worker>,
sender: mpsc::Sender<Job>,
}
impl ThreadPool {
/// Create a new ThreadPool.
///
/// The size is the number of threads in the pool.
///
/// # Panics
///
/// The `new` function will panic if the size is zero.
pub fn new(size: usize) -> ThreadPool {
assert!(size > 0);
let (sender, receiver) = mpsc::channel();
let receiver = Arc::new(Mutex::new(receiver));
let mut workers = Vec::with_capacity(size);
for id in 0..size {
workers.push(Worker::new(id, Arc::clone(&receiver)));
}
ThreadPool { workers, sender }
}
pub fn execute<F>(&self, f: F)
where
F: FnOnce() + Send + 'static,
{
let job = Box::new(f);
self.sender.send(job).unwrap();
}
}
trait FnBox {
fn call_box(self: Box<dyn Self>);
}
impl<F: FnOnce() -> ()> FnBox for F {
fn call_box(self: Box<dyn F>) {
(*self)()
}
}
type Job = Box<dyn FnBox + Send + 'static>;
struct Worker {
id: usize,
thread: thread::JoinHandle<()>,
}
impl Worker {
fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Job>>>) -> Worker {
let thread = thread::spawn(move || loop {
let job = receiver.lock().unwrap().recv().unwrap();
println!("Worker {} got a job; executing.", id);
job.call_box();
});
Worker { id, thread }
}
}
I understand what the errors are saying but i don’t see why the tutorial code generates those. Am i using the wrong rust verstion (stable 1.28) or have i made a dumb mistake i can’t see ?
Thanks in advance