Complete exercise: threads_channels

exercise/threads_channels/src/main.rs

@@ -22,8 +22,8 @@ fn main() {
     // join handle in a variable called `handle`. Once you've done this you should be able to run
     // the code and see the output from the child thread's expensive sum in the middle of the main
     // thread's processing of letters.
-    //
+
-    //let handle = ...
+    let handle = thread::spawn(|| expensive_sum(my_vector));
 
     // While the child thread is running, the main thread will also do some work
     for letter in vec!["a", "b", "c", "d", "e", "f"] {
@@ -37,63 +37,96 @@ fn main() {
     // to a variable named `result`
     // - Get the i32 out of `result` and store it in a `sum` variable.
 
-    // let result =
+    let result = handle.join();
-    // let sum =
+    let sum = result.unwrap();
-    // println!("The child thread's expensive sum is {}", sum);
+    println!("The child thread's expensive sum is {}", sum);
 
     // 3. Time for some fun with channels!
     // - Uncomment the block comment below (Find and remove the `/*` and `*/`).
     // - Create variables `tx` and `rx` and assign them to the sending and receiving ends of an
     // unbounded channel. Hint: An unbounded channel can be created with `channel::unbounded()`
 
-    /*
+    let (tx, rx) = channel::unbounded();
-        // let ...
 
-        // Cloning a channel makes another variable connected to that end of the channel so that you can
+    // Cloning a channel makes another variable connected to that end of the channel so that you can
-        // send it to another thread. We want another variable that can be used for sending...
+    // send it to another thread. We want another variable that can be used for sending...
-        let tx2 = tx.clone();
+    let tx2 = tx.clone();
 
-        // 4. Examine the flow of execution of "Thread A" and "Thread B" below. Do you see how their
+    // 4. Examine the flow of execution of "Thread A" and "Thread B" below. Do you see how their
-        // output will mix with each other?
+    // output will mix with each other?
-        // - Run this code. Notice the order of output from Thread A and Thread B.
+    // - Run this code. Notice the order of output from Thread A and Thread B.
-        // - Increase the value passed to the first `sleep_ms()` call in Thread A so that both the
+    // - Increase the value passed to the first `sleep_ms()` call in Thread A so that both the
-        // Thread B outputs occur *before* Thread A outputs anything.
+    // Thread B outputs occur *before* Thread A outputs anything.
-        // - Run the code again and make sure the output comes in a different order.
+    // - Run the code again and make sure the output comes in a different order.
 
-        // Thread A
+    // Thread A
-        let handle_a = thread::spawn(move || {
+    let handle_a = thread::spawn(move || {
-            sleep_ms(0);
+        sleep_ms(500);
-            tx2.send("Thread A: 1").unwrap();
+        tx2.send("Thread A: 1").unwrap();
-            sleep_ms(200);
+        sleep_ms(200);
-            tx2.send("Thread A: 2").unwrap();
+        tx2.send("Thread A: 2").unwrap();
-        });
+    });
 
-        sleep_ms(100); // Make sure Thread A has time to get going before we spawn Thread B
+    sleep_ms(100); // Make sure Thread A has time to get going before we spawn Thread B
 
-        // Thread B
+    // Thread B
-        let handle_b = thread::spawn(move || {
+    let handle_b = thread::spawn(move || {
-            sleep_ms(0);
+        sleep_ms(0);
-            tx.send("Thread B: 1").unwrap();
+        tx.send("Thread B: 1").unwrap();
-            sleep_ms(200);
+        sleep_ms(200);
-            tx.send("Thread B: 2").unwrap();
+        tx.send("Thread B: 2").unwrap();
-        });
+    });
 
-        // Using a Receiver channel as an iterator is a convenient way to get values until the channel
+    // Using a Receiver channel as an iterator is a convenient way to get values until the channel
-        // gets closed. A Receiver channel is automatically closed once all Sender channels have been
+    // gets closed. A Receiver channel is automatically closed once all Sender channels have been
-        // closed. Both our threads automatically close their Sender channels when they exit and the
+    // closed. Both our threads automatically close their Sender channels when they exit and the
-        // destructors for the channels get automatically called.
+    // destructors for the channels get automatically called.
-        for msg in rx {
+    for msg in rx {
-            println!("Main thread: Received {}", msg);
+        println!("Main thread: Received {}", msg);
-        }
+    }
 
-        // 5. Oops, we forgot to join "Thread A" and "Thread B". That's bad hygiene!
+    // 5. Oops, we forgot to join "Thread A" and "Thread B". That's bad hygiene!
-        // - Use the thread handles to join both threads without getting any compiler warnings.
+    // - Use the thread handles to join both threads without getting any compiler warnings.
-    */
+    let _ = handle_a.join();
+    let _ = handle_b.join();
 
     // Challenge: Make two child threads and give them each a receiving end to a channel. From the
     // main thread loop through several values and print each out and then send it to the channel.
     // On the child threads print out the values you receive. Close the sending side in the main
     // thread by calling `drop(tx)` (assuming you named your sender channel variable `tx`). Join
     // the child threads.
+
+    let (tx, rx) = channel::unbounded();
+    let rx2 = rx.clone();
+
+    let thread_a_handle = thread::spawn(move || {
+        for n in rx {
+            println!("Thread A received: {}", n);
+            sleep_ms(10);
+        }
+    });
+
+    let thread_b_handle = thread::spawn(move || {
+        for n in rx2 {
+            println!("Thread B received: {}", n);
+            sleep_ms(10);
+        }
+    });
+
+    for number in vec![
+        1,
+        2,
+        3,
+        4,
+        5,
+    ] {
+        println!("NUMBER: {}", number);
+        let _ = tx.send(number);
+    }
+    drop(tx);
+
+    let _ = thread_a_handle.join();
+    let _ = thread_b_handle.join();
+
     println!("Main thread: Exiting.")
 }