hyphae 3.0.0

Reactive cells and runtime primitives for rship
Documentation 
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use super::{CellValue, TakeExt};

use crate::pipeline::{Pipeline, Seedness};

#[allow(private_bounds)]
pub trait FirstExt<T: CellValue, S: Seedness>: Pipeline<T, S> + TakeExt<T, S> {
    /// Take only the first value, then complete. Equivalent to `take(1)`.
    #[track_caller]
    fn first(self) -> impl crate::Materialize<T, S> {
        self.take(1)
    }
}

impl<T: CellValue, S: Seedness, P> FirstExt<T, S> for P where P: Pipeline<T, S> + TakeExt<T, S> {}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{Cell, Gettable, Materialize, Mutable, traits::Watchable};

    #[test]
    fn test_first() {
        let source = Cell::new(42);
        let first = source.clone().first().materialize();

        assert_eq!(first.get(), 42);
        assert!(first.is_complete()); // Completes immediately

        source.set(100);
        assert_eq!(first.get(), 42); // Still 42, only takes first
    }
}