search

wolfiestyle / frappe

Functional Reactive Programming library for Rust
MIT License
50 stars 4 forks source link

read Signal without cloning #3

Open dermetfan opened 5 years ago

dermetfan commented 5 years ago

Recently Signal::sample_with() was removed. I was unable to find an alternative to get a reference to the signal's value. This is important to me because I store Strings and other big types in my text editor project.

Is there really no way to get a reference or should I go RTFM?

wolfiestyle commented 5 years ago

The ability to get a reference to the value was removed because it could cause a RefCell borrow violation (in the old version) under some special conditions, and that code was really complex and hard to debug. The new version of Signal doesn't even have that, it's just a function:

pub struct Signal<T>(Arc<dyn Fn() -> T + Send + Sync>);

It's much simpler now, but AFAIK you can't return a reference to closure data. Maybe it can be done with some hack I yet have to research. For now you have to wrap your types on Arc or similar to prevent the cloning (or make them cheap to clone). If you're using strings you may want to look into string interning libraries.