mirror of
https://github.com/rust-lang/rustlings
synced 2024-11-18 09:25:36 +00:00
94 lines
2.6 KiB
Rust
94 lines
2.6 KiB
Rust
// Make this compile! Scroll down for hints :) The idea is the thread
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// spawned on line 17 is completing jobs while the main thread is
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// monitoring progress until 10 jobs are completed. If you see 6 lines
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// of "waiting..." and the program ends without timing out the playground,
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// you've got it :)
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use std::sync::Arc;
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use std::thread;
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struct JobStatus {
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jobs_completed: u32,
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}
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fn main() {
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let status = Arc::new(JobStatus { jobs_completed: 0 });
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let status_shared = status.clone();
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thread::spawn(move || {
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for _ in 0..10 {
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thread::sleep_ms(250);
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status_shared.jobs_completed += 1;
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}
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});
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while status.jobs_completed < 10 {
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println!("waiting... ");
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thread::sleep_ms(500);
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}
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}
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// `Arc` is an Atomic Reference Counted pointer that allows safe, shared access
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// to **immutable** data. But we want to *change* the number of `jobs_completed`
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// so we'll need to also use another type that will only allow one thread to
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// mutate the data at a time. Take a look at this section of the book:
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// https://doc.rust-lang.org/stable/book/concurrency.html#safe-shared-mutable-state
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// and keep scrolling if you'd like more hints :)
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// Do you now have an `Arc` `Mutex` `JobStatus` at the beginning of main? Like:
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// `let status = Arc::new(Mutex::new(JobStatus { jobs_completed: 0 }));`
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// Similar to the code in the example in the book that happens after the text
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// that says "We can use Arc<T> to fix this.". If not, give that a try! If you
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// do and would like more hints, keep scrolling!!
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// Make sure neither of your threads are holding onto the lock of the mutex
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// while they are sleeping, since this will prevent the other thread from
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// being allowed to get the lock. Locks are automatically released when
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// they go out of scope.
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// Ok, so, real talk, this was actually tricky for *me* to do too. And
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// I could see a lot of different problems you might run into, so at this
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// point I'm not sure which one you've hit :) Please see a few possible
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// answers on https://github.com/carols10cents/rustlings/issues/3 --
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// mine is a little more complicated because I decided I wanted to see
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// the number of jobs currently done when I was checking the status.
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// Please open an issue if you're still running into a problem that
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// these hints are not helping you with, or if you've looked at the sample
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// answers and don't understand why they work and yours doesn't.
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// If you've learned from the sample solutions, I encourage you to come
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// back to this exercise and try it again in a few days to reinforce
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// what you've learned :)
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