Struct WithFallback 

pub struct WithFallback<P, F> { /* private fields */ }

Tries the primary strategy first, falls back to secondary if primary returns None.

This is a generic combinator — zero-cost at runtime because both strategies are monomorphised. Use FallbackChain when you need a dynamic list of strategies.

When does fallback trigger?

A strategy returns None when candidates is empty or all candidates are excluded via SelectionContext::exclude. WithFallback is most useful when composed with filtered candidate lists or retry-with-exclude patterns.

Examples

use loadwise::{Strategy, SelectionContext};
use loadwise::strategy::{Random, RoundRobin, WithFallback};

// Prefer random, but fall back to round-robin if it returns None.
let strategy = WithFallback::new(Random::new(), RoundRobin::new());

let nodes = [1, 2, 3];
let ctx = SelectionContext::default();
assert!(strategy.select(&nodes, &ctx).is_some());

Implementations

impl<P, F> WithFallback<P, F>

pub fn new(primary: P, fallback: F) -> Self

Trait Implementations

impl<P: Debug, F: Debug> Debug for WithFallback<P, F>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<N, P, F> Strategy<N> for WithFallback<P, F>

where P: Strategy<N>, F: Strategy<N>,

fn select(&self, candidates: &[N], ctx: &SelectionContext) -> Option<usize>

Pick the next node. Returns None when candidates is empty or all candidates are excluded via SelectionContext::exclude.