Trait mz_repr::RowIterator

source ·

pub trait RowIterator: Debug {
    // Required methods
    fn next(&mut self) -> Option<&RowRef>;
    fn peek(&mut self) -> Option<&RowRef>;
    fn count(&self) -> usize;
    fn box_clone(&self) -> Box<dyn RowIterator>;

    // Provided method
    fn map<T, F>(self, f: F) -> MappedRowIterator<Self, F> ⓘ
       where Self: Sized,
             F: FnMut(&RowRef) -> T { ... }
}

Expand description

An iterator that can borrow from self and yield RowRefs.

This trait is a “lending iterator” for Rows, in other words, an iterator that borrows from self (e.g. an underlying memory buffer) to return a RowRef. The std::iter::Iterator trait does not currently support this pattern because there is no way to name the lifetime of the borrow on its associated Item type. Generic Associated Types (GATs) would allow this but so far no new trait has been introduced with this API.

There are a few open source crates that provide a trait:

Neither have an IntoLendingIterator trait that is useful for our interface, nor do they work well with trait objects.