Initial commit

exercises/20_threads/threads2.rs

@@ -0,0 +1,35 @@
+// Building on the last exercise, we want all of the threads to complete their
+// work. But this time, the spawned threads need to be in charge of updating a
+// shared value: `JobStatus.jobs_done`
+
+use std::{sync::Arc, sync::Mutex, thread, time::Duration};
+
+struct JobStatus {
+    jobs_done: u32,
+}
+
+fn main() {
+    // TODO: `Arc` isn't enough if you want a **mutable** shared state.
+    let status = Arc::new(Mutex::new(JobStatus { jobs_done: 0 }));
+
+    let mut handles = Vec::new();
+    for _ in 0..10 {
+        let status_shared = Arc::clone(&status);
+        let handle = thread::spawn(move || {
+            thread::sleep(Duration::from_millis(250));
+
+            // TODO: You must take an action before you update a shared value.
+            // status_shared.jobs_done += 1;
+            status_shared.lock().unwrap().jobs_done += 1;
+        });
+        handles.push(handle);
+    }
+
+    // Waiting for all jobs to complete.
+    for handle in handles {
+        handle.join().unwrap();
+    }
+
+    // TODO: Print the value of `JobStatus.jobs_done`.
+    println!("Jobs done: {}", status.lock().unwrap().jobs_done);
+}