threads3 solution

exercises/20_threads/threads3.rs

@@ -1,7 +1,4 @@
-use std::sync::mpsc;
-use std::sync::Arc;
-use std::thread;
-use std::time::Duration;
+use std::{sync::mpsc, thread, time::Duration};
 
 struct Queue {
     length: u32,
@@ -11,7 +8,7 @@ struct Queue {
 
 impl Queue {
     fn new() -> Self {
-        Queue {
+        Self {
             length: 10,
             first_half: vec![1, 2, 3, 4, 5],
             second_half: vec![6, 7, 8, 9, 10],
@@ -19,20 +16,22 @@ impl Queue {
     }
 }
 
-fn send_tx(q: Queue, tx: mpsc::Sender<u32>) -> () {
+fn send_tx(q: Queue, tx: mpsc::Sender<u32>) {
+    // TODO: We want to send `tx` to both threads. But currently, it is moved
+    // into the frist thread. How could you solve this problem?
     thread::spawn(move || {
         for val in q.first_half {
-            println!("sending {:?}", val);
+            println!("Sending {val:?}");
             tx.send(val).unwrap();
-            thread::sleep(Duration::from_secs(1));
+            thread::sleep(Duration::from_millis(250));
         }
     });
 
     thread::spawn(move || {
         for val in q.second_half {
-            println!("sending {:?}", val);
+            println!("Sending {val:?}");
             tx.send(val).unwrap();
-            thread::sleep(Duration::from_secs(1));
+            thread::sleep(Duration::from_millis(250));
         }
     });
 }
@@ -55,11 +54,11 @@ mod tests {
 
         let mut total_received: u32 = 0;
         for received in rx {
-            println!("Got: {}", received);
+            println!("Got: {received}");
             total_received += 1;
         }
 
-        println!("total numbers received: {}", total_received);
+        println!("Number of received values: {total_received}");
         assert_eq!(total_received, queue_length);
     }
 }

rustlings-macros/info.toml

@@ -1076,10 +1076,11 @@ An alternate way to handle concurrency between threads is to use an `mpsc`
 With both a sending end and a receiving end, it's possible to send values in
 one thread and receive them in another.
 
-Multiple producers are possible by using clone() to create a duplicate of the
+Multiple producers are possible by using `clone()` to create a duplicate of the
 original sending end.
 
-See https://doc.rust-lang.org/book/ch16-02-message-passing.html for more info."""
+Related section in The Book:
+https://doc.rust-lang.org/book/ch16-02-message-passing.html"""
 
 # MACROS
 

solutions/20_threads/threads3.rs

@@ -1 +1,66 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+use std::{sync::mpsc, thread, time::Duration};
+
+struct Queue {
+    length: u32,
+    first_half: Vec<u32>,
+    second_half: Vec<u32>,
+}
+
+impl Queue {
+    fn new() -> Self {
+        Self {
+            length: 10,
+            first_half: vec![1, 2, 3, 4, 5],
+            second_half: vec![6, 7, 8, 9, 10],
+        }
+    }
+}
+
+fn send_tx(q: Queue, tx: mpsc::Sender<u32>) {
+    // Clone the sender `tx` first.
+    let tx_clone = tx.clone();
+    thread::spawn(move || {
+        for val in q.first_half {
+            println!("Sending {val:?}");
+            // Then use the clone in the first thread. This means that
+            // `tx_clone` is moved to the first thread and `tx` to the second.
+            tx_clone.send(val).unwrap();
+            thread::sleep(Duration::from_millis(250));
+        }
+    });
+
+    thread::spawn(move || {
+        for val in q.second_half {
+            println!("Sending {val:?}");
+            tx.send(val).unwrap();
+            thread::sleep(Duration::from_millis(250));
+        }
+    });
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn threads3() {
+        let (tx, rx) = mpsc::channel();
+        let queue = Queue::new();
+        let queue_length = queue.length;
+
+        send_tx(queue, tx);
+
+        let mut total_received: u32 = 0;
+        for received in rx {
+            println!("Got: {received}");
+            total_received += 1;
+        }
+
+        println!("Number of received values: {total_received}");
+        assert_eq!(total_received, queue_length);
+    }
+}