Struct RuleEngine 

pub struct RuleEngine { /* private fields */ }

The main rule execution engine.

Holds a compiled ruleset and provides methods to execute rules against data.

Performance

The engine pre-sorts rules by priority during construction and performs minimal allocations during execution.

Implementations

impl RuleEngine

pub fn new(ruleset: RuleSet) -> Self

Creates a new rule engine from a ruleset.

Warning Detection

This constructor checks for duplicate priorities within categories and logs warnings if found (order of execution may be non-deterministic).

Examples

use fast_decision::{RuleEngine, RuleSet};
let ruleset: RuleSet = serde_json::from_str(rules_json).unwrap();
let engine = RuleEngine::new(ruleset);

pub fn execute<'a>( &'a self, data: &Value, categories_to_run: &[&str], ) -> Vec<&'a str>

Executes rules from specified categories against the provided data.

Arguments

• data - JSON data to evaluate rules against
• categories_to_run - List of category names to execute

Returns

A vector of rule IDs (as string slices) that matched the data, in priority order.

Behavior

• Rules are evaluated in priority order (lower priority value = higher precedence)
• If a category has stop_on_first: true, execution stops after the first match
• Non-existent categories are silently skipped
• Results accumulate across all requested categories

Performance

• O(n) where n is total number of rules in requested categories
• Pre-allocates result vector with exact capacity
• Minimal allocations during execution

Examples

let data = json!({"user": {"tier": "Gold"}});
let results = engine.execute(&data, &["Pricing", "Fraud"]);
for rule_id in results {
    println!("Matched rule: {}", rule_id);
}