Struct FunctionBindings

pub struct FunctionBindings<'f> { /* private fields */ }

Runtime function bindings.

FunctionBindings manages function implementations during CEL expression evaluation. Unlike FunctionRegistry which is used at compile time, FunctionBindings provides actual callable function implementations for runtime execution.

Each function name can have multiple overloads with different signatures, and each overload can be either a global function or a member function.

Lifetime Parameters

• 'f: Lifetime of function implementations, allowing closures valid within specific scopes

Examples

use cel_cxx::{FunctionBindings, Error};

let mut bindings = FunctionBindings::new();

// Bind global functions
fn add(a: i64, b: i64) -> Result<i64, Error> {
    Ok(a + b)
}
bindings.bind_global("add", add)?;

// Bind member functions
fn string_length(s: String) -> Result<i64, Error> {
    Ok(s.len() as i64)
}
bindings.bind_member("length", string_length)?;

// Bind closures
let multiplier = 10;
let closure = move |x: i64| -> Result<i64, Error> {
    Ok(x * multiplier)
};
bindings.bind_global("multiply_by_ten", closure)?;

Implementations

impl<'f> FunctionBindings<'f>

pub fn new() -> Self

Creates a new empty function bindings.

impl<'f> FunctionBindings<'f>

pub fn bind<F, Fm, Args>( &mut self, name: impl Into<String>, member: bool, f: F, ) -> Result<&mut Self, Error>

where F: IntoFunction<'f, Fm, Args>, Fm: FnMarker, Args: Arguments,

Binds a function implementation with zero-annotation type inference.

Binds a callable function that can be invoked during CEL expression evaluation. The function signature is automatically inferred from the Rust function type, enabling seamless runtime function binding without manual type annotations.

Zero-Annotation Features

• Automatic type inference: Function signature extracted from Rust function type
• Runtime binding: Functions are immediately available for CEL evaluation
• Lifetime handling: Safe conversion of borrowed arguments like &str
• Error conversion: Automatic conversion of Result<T, E> return types
• Async support: Seamless handling of both sync and async functions

Type Parameters

• F: Function type, must implement IntoFunction
• Fm: Function marker (sync or async), automatically inferred
• Args: Argument tuple type, automatically inferred from function signature

Parameters

• name: Function name
• member: Whether this is a member function (true) or global function (false)
• f: Function implementation

Returns

Returns &mut Self to support method chaining

Examples

Basic function binding with automatic type inference

use cel_cxx::FunctionBindings;

let mut bindings = FunctionBindings::new();

// Zero-annotation function binding
bindings.bind("multiply", false, |a: i64, b: i64| a * b)?;
bindings.bind("upper", true, |s: String| s.to_uppercase())?;
bindings.bind("contains", true, |s: &str, substr: &str| s.contains(substr))?;

Runtime function binding with closures

use cel_cxx::FunctionBindings;

let mut bindings = FunctionBindings::new();
let multiplier = 10;

// Bind closure that captures environment
bindings.bind("scale", false, move |x: i64| x * multiplier)?;

pub fn bind_member<F, Fm, Args>( &mut self, name: impl Into<String>, f: F, ) -> Result<&mut Self, Error>

where F: IntoFunction<'f, Fm, Args>, Fm: FnMarker, Args: Arguments,

Binds a member function implementation.

Convenience method for binding member functions that can be called as methods on values (e.g., "hello".upper()).

Examples

use cel_cxx::{FunctionBindings, Error};

let mut bindings = FunctionBindings::new();

fn reverse(s: String) -> Result<String, Error> {
    Ok(s.chars().rev().collect())
}

bindings.bind_member("reverse", reverse)?;

pub fn bind_global<F, Fm, Args>( &mut self, name: impl Into<String>, f: F, ) -> Result<&mut Self, Error>

where F: IntoFunction<'f, Fm, Args>, Fm: FnMarker, Args: Arguments,

Binds a global function implementation.

Convenience method for binding global functions that can be called from any context.

Examples

use cel_cxx::{FunctionBindings, Error};

let mut bindings = FunctionBindings::new();

fn min(a: i64, b: i64) -> Result<i64, Error> {
    Ok(a.min(b))
}

bindings.bind_global("min", min)?;

pub fn find(&self, name: &str) -> Option<&FunctionOverloads<Function<'f>>>

Finds a function overload set by name.

Parameters

• name: Function name to search for

Returns

Returns Some(&FunctionOverloads) if found, None otherwise

pub fn find_mut( &mut self, name: &str, ) -> Option<&mut FunctionOverloads<Function<'f>>>

Finds a mutable function overload set by name.

Parameters

• name: Function name to search for

Returns

Returns Some(&mut FunctionOverloads) if found, None otherwise

pub fn entries( &self, ) -> impl Iterator<Item = (&str, &FunctionOverloads<Function<'f>>)>

Returns an iterator over all function entries.

The iterator yields (name, overloads) pairs for all bound functions.

pub fn entries_mut( &mut self, ) -> impl Iterator<Item = (&str, &mut FunctionOverloads<Function<'f>>)>

Returns a mutable iterator over all function entries.

The iterator yields (name, overloads) pairs and allows modifying the overloads.

pub fn remove(&mut self, name: &str) -> Result<(), Error>

Removes a function by name.

Parameters

• name: Function name to remove

Returns

Returns Ok(()) if successfully removed, or an error if the function doesn’t exist

pub fn clear(&mut self)

Clears all function bindings.

Trait Implementations

impl<'f> Debug for FunctionBindings<'f>

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

Formats the value using the given formatter.

impl<'f> Default for FunctionBindings<'f>

fn default() -> FunctionBindings<'f>

Returns the “default value” for a type.