Trait PredicateVisitor 

pub trait PredicateVisitor {
    type Error;
    type Value;

    // Required methods
    fn visit_leaf(
        &mut self,
        leaf: &PredicateNode,
    ) -> Result<VisitOutcome<Self::Value>, Self::Error>;
    fn combine_not(
        &mut self,
        original: &Predicate,
        child: VisitOutcome<Self::Value>,
    ) -> Result<VisitOutcome<Self::Value>, Self::Error>;
    fn combine_and(
        &mut self,
        original: &Predicate,
        children: Vec<VisitOutcome<Self::Value>>,
    ) -> Result<VisitOutcome<Self::Value>, Self::Error>;
    fn combine_or(
        &mut self,
        original: &Predicate,
        children: Vec<VisitOutcome<Self::Value>>,
    ) -> Result<VisitOutcome<Self::Value>, Self::Error>;

    // Provided methods
    fn visit_predicate(
        &mut self,
        predicate: &Predicate,
    ) -> Result<VisitOutcome<Self::Value>, Self::Error> { ... }
    fn visit_node(
        &mut self,
        node: &PredicateNode,
        original: &Predicate,
    ) -> Result<VisitOutcome<Self::Value>, Self::Error> { ... }
}

Visitor that walks predicate trees and emits custom results plus residual predicates.

Required Associated Types

type Error

Error type used when evaluation fails.

type Value

Concrete value type produced while walking the predicate.

Required Methods

fn visit_leaf( &mut self, leaf: &PredicateNode, ) -> Result<VisitOutcome<Self::Value>, Self::Error>

Evaluates a leaf predicate and returns its result.

fn combine_not( &mut self, original: &Predicate, child: VisitOutcome<Self::Value>, ) -> Result<VisitOutcome<Self::Value>, Self::Error>

Combines the result of a negated child predicate.

fn combine_and( &mut self, original: &Predicate, children: Vec<VisitOutcome<Self::Value>>, ) -> Result<VisitOutcome<Self::Value>, Self::Error>

Combines an AND clause from the supplied child results.

fn combine_or( &mut self, original: &Predicate, children: Vec<VisitOutcome<Self::Value>>, ) -> Result<VisitOutcome<Self::Value>, Self::Error>

Combines an OR clause from the supplied child results.

Provided Methods

fn visit_predicate( &mut self, predicate: &Predicate, ) -> Result<VisitOutcome<Self::Value>, Self::Error>

Visits the supplied predicate by walking the expression tree.

fn visit_node( &mut self, node: &PredicateNode, original: &Predicate, ) -> Result<VisitOutcome<Self::Value>, Self::Error>

Internal helper that evaluates a predicate node recursively.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors