132 lines
4.1 KiB
Rust
132 lines
4.1 KiB
Rust
//! Module that defines the `Scope` type representing a function call-stack scope.
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use crate::any::{Any, Dynamic};
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use std::borrow::Cow;
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/// A type containing information about current scope.
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/// Useful for keeping state between `Engine` runs.
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///
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/// # Example
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///
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/// ```rust
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/// # fn main() -> Result<(), rhai::EvalAltResult> {
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/// use rhai::{Engine, Scope};
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///
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/// let mut engine = Engine::new();
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/// let mut my_scope = Scope::new();
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///
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/// engine.eval_with_scope::<()>(&mut my_scope, "let x = 5;")?;
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///
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/// assert_eq!(engine.eval_with_scope::<i64>(&mut my_scope, "x + 1")?, 6);
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/// # Ok(())
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/// # }
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/// ```
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///
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/// When searching for variables, newly-added variables are found before similarly-named but older variables,
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/// allowing for automatic _shadowing_ of variables.
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pub struct Scope<'a>(Vec<(Cow<'a, str>, Dynamic)>);
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impl<'a> Scope<'a> {
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/// Create a new Scope.
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pub fn new() -> Self {
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Self(Vec::new())
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}
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/// Empty the Scope.
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pub fn clear(&mut self) {
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self.0.clear();
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}
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/// Get the number of variables inside the Scope.
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pub fn len(&self) -> usize {
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self.0.len()
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}
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/// Add (push) a new variable to the Scope.
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pub fn push<K: Into<Cow<'a, str>>, T: Any>(&mut self, key: K, value: T) {
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self.0.push((key.into(), Box::new(value)));
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}
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/// Add (push) a new variable to the Scope.
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pub(crate) fn push_dynamic<K: Into<Cow<'a, str>>>(&mut self, key: K, value: Dynamic) {
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self.0.push((key.into(), value));
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}
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/// Remove (pop) the last variable from the Scope.
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pub fn pop(&mut self) -> Option<(String, Dynamic)> {
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self.0.pop().map(|(key, value)| (key.to_string(), value))
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}
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/// Truncate (rewind) the Scope to a previous size.
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pub fn rewind(&mut self, size: usize) {
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self.0.truncate(size);
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}
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/// Find a variable in the Scope, starting from the last.
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pub fn get(&self, key: &str) -> Option<(usize, &str, Dynamic)> {
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self.0
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.iter()
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.enumerate()
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.rev() // Always search a Scope in reverse order
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.find(|(_, (name, _))| name == key)
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.map(|(i, (name, value))| (i, name.as_ref(), value.clone()))
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}
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/// Get the value of a variable in the Scope, starting from the last.
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pub fn get_value<T: Any + Clone>(&self, key: &str) -> Option<T> {
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self.0
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.iter()
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.enumerate()
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.rev() // Always search a Scope in reverse order
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.find(|(_, (name, _))| name == key)
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.and_then(|(_, (_, value))| value.downcast_ref::<T>())
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.map(|value| value.clone())
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}
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/// Get a mutable reference to a variable in the Scope.
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pub(crate) fn get_mut(&mut self, key: &str, index: usize) -> &mut Dynamic {
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let entry = self.0.get_mut(index).expect("invalid index in Scope");
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assert_eq!(entry.0, key, "incorrect key at Scope entry");
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&mut entry.1
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}
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/// Get a mutable reference to a variable in the Scope and downcast it to a specific type
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#[cfg(not(feature = "no_index"))]
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pub(crate) fn get_mut_by_type<T: Any + Clone>(&mut self, key: &str, index: usize) -> &mut T {
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self.get_mut(key, index)
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.downcast_mut::<T>()
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.expect("wrong type cast")
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}
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/// Get an iterator to variables in the Scope.
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pub fn iter(&self) -> impl Iterator<Item = (&str, &Dynamic)> {
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self.0
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.iter()
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.rev() // Always search a Scope in reverse order
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.map(|(key, value)| (key.as_ref(), value))
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}
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/*
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/// Get a mutable iterator to variables in the Scope.
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pub fn iter_mut(&mut self) -> impl Iterator<Item = (&str, &mut Dynamic)> {
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self.0
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.iter_mut()
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.rev() // Always search a Scope in reverse order
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.map(|(key, value)| (key.as_ref(), value))
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}
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*/
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}
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impl<'a, K> std::iter::Extend<(K, Dynamic)> for Scope<'a>
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where
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K: Into<Cow<'a, str>>,
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{
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fn extend<T: IntoIterator<Item = (K, Dynamic)>>(&mut self, iter: T) {
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self.0
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.extend(iter.into_iter().map(|(key, value)| (key.into(), value)));
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}
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}
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