33 lines
893 B
Markdown
33 lines
893 B
Markdown
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Throw Exception on Error
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=======================
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{{#include ../links.md}}
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All of [`Engine`]'s evaluation/consuming methods return `Result<T, Box<rhai::EvalAltResult>>`
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with `EvalAltResult` holding error information.
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To deliberately return an error during an evaluation, use the `throw` keyword.
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```rust
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if some_bad_condition_has_happened {
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throw error; // 'throw' takes a string as the exception text
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}
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throw; // defaults to empty exception text: ""
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```
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Exceptions thrown via `throw` in the script can be captured by matching `Err(Box<EvalAltResult::ErrorRuntime(` _reason_ `,` _position_ `)>)`
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with the exception text captured by the first parameter.
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```rust
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let result = engine.eval::<i64>(r#"
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let x = 42;
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if x > 0 {
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throw x + " is too large!";
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}
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"#);
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println!(result); // prints "Runtime error: 42 is too large! (line 5, position 15)"
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```
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