Struct NestedListFieldExtractor 

pub struct NestedListFieldExtractor { /* private fields */ }

Extracts a list of scalar values from a nested Vec<T> field using a path.

This enables FanOut-style extraction for lists within nested structures.

Example

use serde::Serialize;
use serde_evaluate::{NestedListFieldExtractor, FieldScalarValue, EvaluateError};

#[derive(Serialize)]
struct Record {
    metadata: Metadata,
}

#[derive(Serialize)]
struct Metadata {
    labels: Vec<String>,
}

fn main() -> Result<(), EvaluateError> {
    let record = Record {
        metadata: Metadata {
            labels: vec!["label1".to_string(), "label2".to_string()],
        },
    };

    let extractor = NestedListFieldExtractor::new_from_path(&["metadata", "labels"])?;
    let values = extractor.evaluate(&record)?;

    assert_eq!(values, vec![
        FieldScalarValue::String("label1".to_string()),
        FieldScalarValue::String("label2".to_string()),
    ]);
    Ok(())
}

Implementations

impl NestedListFieldExtractor

pub fn new_from_path<S: AsRef<str>>( path_segments: &[S], ) -> Result<Self, EvaluateError>

Creates a new NestedListFieldExtractor from a slice of path segments.

Each element in the input slice represents a step in the path.

Arguments

• path_segments: A slice where each element can be converted into a &str (e.g., &str, String).

Errors

Returns EvaluateError::InvalidPath if the input slice is empty or if any segment converts to an empty string.

pub fn evaluate<T: Serialize>( &self, value: &T, ) -> Result<Vec<FieldScalarValue>, EvaluateError>

Extracts all scalar elements from a nested Vec<T> field.

Arguments

• value - A reference to a value that implements serde::Serialize.

Returns

• Ok(Vec<FieldScalarValue>) containing each element as a scalar value.
• Ok(vec![]) for empty lists or Option<Vec<T>> with None.

Errors

Returns EvaluateError if:

• The path is not found (EvaluateError::NestedFieldNotFound).
• The list elements are not scalar types (EvaluateError::UnsupportedType).

Trait Implementations

impl Clone for NestedListFieldExtractor

fn clone(&self) -> NestedListFieldExtractor

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for NestedListFieldExtractor

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

Formats the value using the given formatter.