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32 lines
975 B
Markdown
32 lines
975 B
Markdown
# Simple Chained String Errors
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With relatively small changes and the help of the `cherr!` macro of the `chainerror` crate
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the `String` errors are now chained together.
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Press the play button in the upper right corner and see the nice debug output.
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~~~rust
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{{#include ../examples/tutorial2.rs}}
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# #[allow(dead_code)]
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# mod chainerror {
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{{#includecomment ../src/lib.rs}}
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# }
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~~~
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### What did we do here?
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~~~rust,ignore
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{{#include ../examples/tutorial2.rs:13:15}}
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~~~
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The macro `cherr!(olderror, newerror)` stores `olderror` as the source/cause of `newerror`
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along with the filename (`file!()`) and line number (`line!()`)
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and returns `newerror`.
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`Err()?` then returns the inner error applying `.into()`, so that we
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again have a `Err(Box<Error>)` as a result.
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The `Debug` implementation of `ChainError<T>` (which is returned by `cherr!()`)
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prints the `Debug` of `T` prefixed with the stored filename and line number.
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`ChainError<T>` in our case is `ChainError<String>`. |