22 lines
983 B
Markdown
22 lines
983 B
Markdown
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`String` Parameters in Rust Functions
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====================================
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{{#include ../links.md}}
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Rust functions accepting parameters of `String` should use `&str` instead because it maps directly to [`ImmutableString`]
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which is the type that Rhai uses to represent [strings] internally.
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```rust
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fn get_len1(s: String) -> i64 { s.len() as i64 } // <- Rhai will not find this function
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fn get_len2(s: &str) -> i64 { s.len() as i64 } // <- Rhai finds this function fine
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fn get_len3(s: ImmutableString) -> i64 { s.len() as i64 } // <- the above is equivalent to this
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engine.register_fn("len1", get_len1);
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engine.register_fn("len2", get_len2);
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engine.register_fn("len3", get_len3);
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let len = engine.eval::<i64>("x.len1()")?; // error: function 'len1 (&str | ImmutableString)' not found
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let len = engine.eval::<i64>("x.len2()")?; // works fine
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let len = engine.eval::<i64>("x.len3()")?; // works fine
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```
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