43 lines
1.3 KiB
Rust
43 lines
1.3 KiB
Rust
//! This example stores a Rhai closure for later use as a callback.
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use rhai::{Engine, EvalAltResult, FnPtr};
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// To call a Rhai closure at a later time, you'd need three things:
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// 1) an `Engine` (with all needed functions registered),
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// 2) a compiled `AST`,
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// 3) the closure (of type `FnPtr`).
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fn main() -> Result<(), Box<EvalAltResult>> {
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let engine = Engine::new();
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// This script creates a closure which captures a variable and returns it.
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let ast = engine.compile(
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"
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let x = 18;
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// The following closure captures 'x'
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return |a, b| {
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x += 1; // x is incremented each time
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(x + a) * b
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};
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",
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)?;
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let closure = engine.eval_ast::<FnPtr>(&ast)?;
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// Create a closure by encapsulating the `Engine`, `AST` and `FnPtr`.
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// In a real application, you'd be handling errors.
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let func = move |x: i64, y: i64| -> i64 { closure.call(&engine, &ast, (x, y)).unwrap() };
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// Now we can call `func` anywhere just like a normal function!
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let r1 = func(1, 2);
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// Notice that each call to `func` returns a different value
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// because the captured `x` is always changing!
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let r2 = func(1, 2);
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let r3 = func(1, 2);
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println!("The Answers: {r1}, {r2}, {r3}"); // prints 40, 42, 44
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Ok(())
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}
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