65 lines
2.4 KiB
Markdown
65 lines
2.4 KiB
Markdown
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Calling Rhai Functions from Rust
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===============================
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{{#include ../links.md}}
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Rhai also allows working _backwards_ from the other direction - i.e. calling a Rhai-scripted function
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from Rust via `Engine::call_fn`.
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Functions declared with `private` are hidden and cannot be called from Rust (see also [modules]).
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```rust
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// Define functions in a script.
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let ast = engine.compile(true,
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r#"
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// a function with two parameters: string and i64
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fn hello(x, y) {
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x.len + y
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}
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// functions can be overloaded: this one takes only one parameter
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fn hello(x) {
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x * 2
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}
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// this one takes no parameters
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fn hello() {
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42
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}
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// this one is private and cannot be called by 'call_fn'
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private hidden() {
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throw "you shouldn't see me!";
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}
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"#)?;
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// A custom scope can also contain any variables/constants available to the functions
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let mut scope = Scope::new();
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// Evaluate a function defined in the script, passing arguments into the script as a tuple.
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// Beware, arguments must be of the correct types because Rhai does not have built-in type conversions.
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// If arguments of the wrong types are passed, the Engine will not find the function.
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let result: i64 = engine.call_fn(&mut scope, &ast, "hello", ( String::from("abc"), 123_i64 ) )?;
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// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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// put arguments in a tuple
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let result: i64 = engine.call_fn(&mut scope, &ast, "hello", (123_i64,) )?;
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// ^^^^^^^^^^ tuple of one
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let result: i64 = engine.call_fn(&mut scope, &ast, "hello", () )?;
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// ^^ unit = tuple of zero
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// The following call will return a function-not-found error because
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// 'hidden' is declared with 'private'.
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let result: () = engine.call_fn(&mut scope, &ast, "hidden", ())?;
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```
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For more control, construct all arguments as `Dynamic` values and use `Engine::call_fn_dynamic`, passing it
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anything that implements `IntoIterator<Item = Dynamic>` (such as a simple `Vec<Dynamic>`):
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```rust
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let result: Dynamic = engine.call_fn_dynamic(&mut scope, &ast, "hello",
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vec![ String::from("abc").into(), 123_i64.into() ])?;
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```
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