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Add support for custom type indexers.

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This commit is contained in:
Stephen Chung 2020-05-05 20:38:48 +08:00
parent 798e1df298
commit f081040767
5 changed files with 144 additions and 23 deletions
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37
README.md
View File

@ -15,7 +15,7 @@ Rhai's current features set:
* Easy-to-use language similar to JS+Rust
* Easy integration with Rust [native functions](#working-with-functions) and [types](#custom-types-and-methods),
including [getter/setter](#getters-and-setters)/[methods](#members-and-methods)
including [getters/setters](#getters-and-setters), [methods](#members-and-methods) and [indexers](#indexers)
* Easily [call a script-defined function](#calling-rhai-functions-from-rust) from Rust
* Freely pass variables/constants into a script via an external [`Scope`]
* Fairly efficient (1 million iterations in 0.75 sec on my 5 year old laptop)
@ -923,6 +923,41 @@ let result = engine.eval::<i64>("let a = new_ts(); a.xyz = 42; a.xyz")?;
println!("Answer: {}", result); // prints 42
```
Indexers
--------
Custom types can also expose an _indexer_ by registering an indexer function.
A custom with an indexer function defined can use the bracket '`[]`' notation to get a property value
(but not update it - indexers are read-only).
```rust
#[derive(Clone)]
struct TestStruct {
fields: Vec<i64>
}
impl TestStruct {
fn get_field(&mut self, index: i64) -> i64 {
self.field
}
fn new() -> Self {
TestStruct { field: vec![1, 2, 42, 4, 5] }
}
}
let engine = Engine::new();
engine.register_type::<TestStruct>();
engine.register_fn("new_ts", TestStruct::new);
engine.register_indexer(TestStruct::get_field);
let result = engine.eval::<i64>("let a = new_ts(); a[2]")?;
println!("Answer: {}", result); // prints 42
```
Needless to say, `register_type`, `register_type_with_name`, `register_get`, `register_set` and `register_get_set`
are not available when the [`no_object`] feature is turned on.

60
src/api.rs
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@ -1,7 +1,7 @@
//! Module that defines the extern API of `Engine`.
use crate::any::{Dynamic, Variant};
use crate::engine::{make_getter, make_setter, Engine, Map, State};
use crate::engine::{make_getter, make_setter, Engine, Map, State, FUNC_INDEXER};
use crate::error::ParseError;
use crate::fn_call::FuncArgs;
use crate::fn_register::RegisterFn;
@ -42,6 +42,16 @@ pub trait ObjectSetCallback<T, U>: Fn(&mut T, U) + 'static {}
#[cfg(not(feature = "sync"))]
impl<F: Fn(&mut T, U) + 'static, T, U> ObjectSetCallback<T, U> for F {}
#[cfg(feature = "sync")]
pub trait ObjectIndexerCallback<T, X, U>: Fn(&mut T, X) -> U + Send + Sync + 'static {}
#[cfg(feature = "sync")]
impl<F: Fn(&mut T, X) -> U + Send + Sync + 'static, T, X, U> ObjectIndexerCallback<T, X, U> for F {}
#[cfg(not(feature = "sync"))]
pub trait ObjectIndexerCallback<T, X, U>: Fn(&mut T, X) -> U + 'static {}
#[cfg(not(feature = "sync"))]
impl<F: Fn(&mut T, X) -> U + 'static, T, X, U> ObjectIndexerCallback<T, X, U> for F {}
#[cfg(feature = "sync")]
pub trait IteratorCallback:
Fn(Dynamic) -> Box<dyn Iterator<Item = Dynamic>> + Send + Sync + 'static
@ -299,6 +309,54 @@ impl Engine {
self.register_set(name, set_fn);
}
/// Register an indexer function for a registered type with the `Engine`.
///
/// The function signature must start with `&mut self` and not `&self`.
///
/// # Example
///
/// ```
/// #[derive(Clone)]
/// struct TestStruct {
/// fields: Vec<i64>
/// }
///
/// impl TestStruct {
/// fn new() -> Self { TestStruct { fields: vec![1, 2, 3, 4, 5] } }
///
/// // Even a getter must start with `&mut self` and not `&self`.
/// fn get_field(&mut self, index: i64) -> i64 { self.fields[index as usize] }
/// }
///
/// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
/// use rhai::{Engine, RegisterFn};
///
/// let mut engine = Engine::new();
///
/// // Register the custom type.
/// engine.register_type::<TestStruct>();
///
/// engine.register_fn("new_ts", TestStruct::new);
///
/// // Register an indexer.
/// engine.register_indexer(TestStruct::get_field);
///
/// assert_eq!(engine.eval::<i64>("let a = new_ts(); a[2]")?, 3);
/// # Ok(())
/// # }
/// ```
#[cfg(not(feature = "no_object"))]
#[cfg(not(feature = "no_index"))]
pub fn register_indexer<T, X, U, F>(&mut self, callback: F)
where
T: Variant + Clone,
U: Variant + Clone,
X: Variant + Clone,
F: ObjectIndexerCallback<T, X, U>,
{
self.register_fn(FUNC_INDEXER, callback);
}
/// Compile a string into an `AST`, which can be used later for evaluation.
///
/// # Example

53
src/engine.rs
View File

@ -74,6 +74,7 @@ pub const KEYWORD_EVAL: &str = "eval";
pub const FUNC_TO_STRING: &str = "to_string";
pub const FUNC_GETTER: &str = "get$";
pub const FUNC_SETTER: &str = "set$";
pub const FUNC_INDEXER: &str = "$index$";
/// A type that encapsulates a mutation target for an expression with side effects.
enum Target<'a> {
@ -577,6 +578,11 @@ impl Engine {
});
}
// Return default value (if any)
if let Some(val) = def_val {
return Ok(val.clone());
}
// Getter function not found?
if let Some(prop) = extract_prop_from_getter(fn_name) {
return Err(Box::new(EvalAltResult::ErrorDotExpr(
@ -593,17 +599,20 @@ impl Engine {
)));
}
// Return default value (if any)
if let Some(val) = def_val {
return Ok(val.clone());
}
// Raise error
let types_list: Vec<_> = args
.iter()
.map(|name| self.map_type_name(name.type_name()))
.collect();
// Getter function not found?
if fn_name == FUNC_INDEXER {
return Err(Box::new(EvalAltResult::ErrorFunctionNotFound(
format!("[]({})", types_list.join(", ")),
pos,
)));
}
// Raise error
Err(Box::new(EvalAltResult::ErrorFunctionNotFound(
format!("{} ({})", fn_name, types_list.join(", ")),
pos,
@ -787,20 +796,20 @@ impl Engine {
Expr::Index(idx, idx_rhs, pos) => {
let is_index = matches!(rhs, Expr::Index(_,_,_));
let indexed_val = self.get_indexed_mut(obj, idx_val, idx.position(), op_pos, false)?;
let indexed_val = self.get_indexed_mut(fn_lib, obj, idx_val, idx.position(), op_pos, false)?;
self.eval_dot_index_chain_helper(
fn_lib, indexed_val, idx_rhs.as_ref(), idx_values, is_index, *pos, level, new_val
)
}
// xxx[rhs] = new_val
_ if new_val.is_some() => {
let mut indexed_val = self.get_indexed_mut(obj, idx_val, rhs.position(), op_pos, true)?;
let mut indexed_val = self.get_indexed_mut(fn_lib, obj, idx_val, rhs.position(), op_pos, true)?;
indexed_val.set_value(new_val.unwrap(), rhs.position())?;
Ok((Default::default(), true))
}
// xxx[rhs]
_ => self
.get_indexed_mut(obj, idx_val, rhs.position(), op_pos, false)
.get_indexed_mut(fn_lib, obj, idx_val, rhs.position(), op_pos, false)
.map(|v| (v.clone_into_dynamic(), false))
}
} else {
@ -818,14 +827,14 @@ impl Engine {
// {xxx:map}.id = ???
Expr::Property(id, pos) if obj.is::<Map>() && new_val.is_some() => {
let mut indexed_val =
self.get_indexed_mut(obj, id.to_string().into(), *pos, op_pos, true)?;
self.get_indexed_mut(fn_lib, obj, id.to_string().into(), *pos, op_pos, true)?;
indexed_val.set_value(new_val.unwrap(), rhs.position())?;
Ok((Default::default(), true))
}
// {xxx:map}.id
Expr::Property(id, pos) if obj.is::<Map>() => {
let indexed_val =
self.get_indexed_mut(obj, id.to_string().into(), *pos, op_pos, false)?;
self.get_indexed_mut(fn_lib, obj, id.to_string().into(), *pos, op_pos, false)?;
Ok((indexed_val.clone_into_dynamic(), false))
}
// xxx.id = ???
@ -847,7 +856,7 @@ impl Engine {
let is_index = matches!(rhs, Expr::Index(_,_,_));
let indexed_val = if let Expr::Property(id, pos) = dot_lhs.as_ref() {
self.get_indexed_mut(obj, id.to_string().into(), *pos, op_pos, false)?
self.get_indexed_mut(fn_lib, obj, id.to_string().into(), *pos, op_pos, false)?
} else {
// Syntax error
return Err(Box::new(EvalAltResult::ErrorDotExpr(
@ -1010,8 +1019,9 @@ impl Engine {
/// Get the value at the indexed position of a base type
fn get_indexed_mut<'a>(
&self,
fn_lib: &FunctionsLib,
val: &'a mut Dynamic,
idx: Dynamic,
mut idx: Dynamic,
idx_pos: Position,
op_pos: Position,
create: bool,
@ -1084,11 +1094,18 @@ impl Engine {
}
}
// Error - cannot be indexed
_ => Err(Box::new(EvalAltResult::ErrorIndexingType(
type_name.to_string(),
op_pos,
))),
_ => {
let args = &mut [val, &mut idx];
self.exec_fn_call(fn_lib, FUNC_INDEXER, args, None, op_pos, 0)
.map(|v| v.into())
.map_err(|_| {
Box::new(EvalAltResult::ErrorIndexingType(
// Error - cannot be indexed
type_name.to_string(),
op_pos,
))
})
}
}
}

4
src/result.rs
View File

@ -47,7 +47,7 @@ pub enum EvalAltResult {
/// String indexing out-of-bounds.
/// Wrapped values are the current number of characters in the string and the index number.
ErrorStringBounds(usize, INT, Position),
/// Trying to index into a type that is not an array, an object map, or a string.
/// Trying to index into a type that is not an array, an object map, or a string, and has no indexer function defined.
ErrorIndexingType(String, Position),
/// Trying to index into an array or string with an index that is not `i64`.
ErrorNumericIndexExpr(Position),
@ -104,7 +104,7 @@ impl EvalAltResult {
}
Self::ErrorStringIndexExpr(_) => "Indexing into an object map expects a string index",
Self::ErrorIndexingType(_, _) => {
"Indexing can only be performed on an array, an object map, or a string"
"Indexing can only be performed on an array, an object map, a string, or a type with an indexer function defined"
}
Self::ErrorArrayBounds(_, index, _) if *index < 0 => {
"Array access expects non-negative index"

13
tests/get_set.rs
View File

@ -8,6 +8,7 @@ fn test_get_set() -> Result<(), Box<EvalAltResult>> {
struct TestStruct {
x: INT,
y: INT,
array: Vec<INT>,
}
impl TestStruct {
@ -24,7 +25,11 @@ fn test_get_set() -> Result<(), Box<EvalAltResult>> {
}
fn new() -> Self {
TestStruct { x: 1, y: 0 }
TestStruct {
x: 1,
y: 0,
array: vec![1, 2, 3, 4, 5],
}
}
}
@ -37,10 +42,16 @@ fn test_get_set() -> Result<(), Box<EvalAltResult>> {
engine.register_fn("add", |value: &mut INT| *value += 41);
engine.register_fn("new_ts", TestStruct::new);
#[cfg(not(feature = "no_index"))]
engine.register_indexer(|value: &mut TestStruct, index: INT| value.array[index as usize]);
assert_eq!(engine.eval::<INT>("let a = new_ts(); a.x = 500; a.x")?, 500);
assert_eq!(engine.eval::<INT>("let a = new_ts(); a.x.add(); a.x")?, 42);
assert_eq!(engine.eval::<INT>("let a = new_ts(); a.y.add(); a.y")?, 0);
#[cfg(not(feature = "no_index"))]
assert_eq!(engine.eval::<INT>("let a = new_ts(); a[3]")?, 4);
Ok(())
}