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34 lines
883 B
Markdown
34 lines
883 B
Markdown
# Selective Error Handling
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What about functions returning different Error types?
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In this example `func1()` can return either `Func1ErrorFunc2` or `Func1ErrorIO`.
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We might want to `match` on `func1()` with something like:
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~~~rust,ignore
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fn main() -> Result<(), Box<Error + Send + Sync>> {
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match func1() {
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Err(e) if let Some(s) = e.downcast_chain_ref::<Func1ErrorIO>() =>
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eprintln!("Func1ErrorIO:\n{:?}", s),
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Err(e) if let Some(s) = e.downcast_chain_ref::<Func1ErrorFunc2>() =>
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eprintln!("Func1ErrorFunc2:\n{:?}", s),
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Ok(_) => {},
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}
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Ok(())
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}
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~~~
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but this is not valid rust code, so we end up doing it the hard way.
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In the next chapter, we will see, how to solve this more elegantly.
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~~~rust
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{{#include ../examples/tutorial9.rs}}
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# #[allow(dead_code)]
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# mod chainerror {
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{{#rustdoc_include ../src/lib.rs:-1}}
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# }
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~~~
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