Function filter

pub fn filter<'a, Pred, Output, FnArgs, Descr>(
    pred: Pred,
) -> Handler<'a, Output, Descr>
where
    Asyncify<Pred>: Injectable<bool, FnArgs> + Send + Sync + 'a,
    Output: 'a,
    Descr: HandlerDescription,

Constructs a handler that filters input with the predicate pred.

pred has an access to all values that are stored in the input container. If it returns true, a continuation of the handler will be called, otherwise the handler returns ControlFlow::Continue.