Struct Expression

pub struct Expression<'env, 'source> { /* private fields */ }

A handle to a compiled expression.

An expression is created via the compile_expression method. It provides a method to evaluate the expression and return the result as value object. This for instance can be used to evaluate simple expressions from user provided input to implement features such as dynamic filtering.

This is usually best paired with context to pass a single value to it.

Example

let env = Environment::new();
let expr = env.compile_expression("number > 10 and number < 20").unwrap();
let rv = expr.eval(context!(number => 15)).unwrap();
assert!(rv.is_true());

Implementations

impl<'env, 'source> Expression<'env, 'source>

pub fn eval<S>(&self, ctx: S) -> Result<Value, Error>

where S: Serialize,

Evaluates the expression with some context.

The result of the expression is returned as Value.

pub fn undeclared_variables(&self, nested: bool) -> HashSet<String>

Returns a set of all undeclared variables in the expression.

This works the same as Template::undeclared_variables.

Trait Implementations

impl<'env, 'source> Debug for Expression<'env, 'source>

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

Formats the value using the given formatter.