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35 lines
1.1 KiB
Markdown
35 lines
1.1 KiB
Markdown
# The root cause of all Errors
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`chainerror` also has some helper methods:
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~~~rust,ignore
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fn is_chain<T: 'static + Display + Debug>(&self) -> bool
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fn downcast_chain_ref<T: 'static + Display + Debug>(&self) -> Option<&chainerror::Error<T>>
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fn downcast_chain_mut<T: 'static + Display + Debug>(&mut self) -> Option<&mut chainerror::Error<T>>
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fn root_cause(&self) -> Option<&(dyn Error + 'static)>
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fn find_cause<U: Error + 'static>(&self) -> Option<&U>
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fn find_chain_cause<U: Error + 'static>(&self) -> Option<&chainerror::Error<U>>
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fn kind<'a>(&'a self) -> &'a T
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~~~
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Using `downcast_chain_ref::<String>()` gives a `chainerror::Error<String>`, which can be used
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to call `.find_cause::<io::Error>()`.
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~~~rust,ignore
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if let Some(s) = e.downcast_chain_ref::<String>() {
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if let Some(ioerror) = s.find_cause::<io::Error>() {
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~~~
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or to use `.root_cause()`, which of course can be of any type implementing `std::error::Error`.
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~~~rust,ignore
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if let Some(e) = s.root_cause() {
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~~~
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~~~rust
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{{#include ../examples/tutorial7.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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~~~ |