2018-12-20 15:14:21 +01:00
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## Simple Chained String Errors
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Now with the help of the `chainerror` crate, we can have a nicer output.
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Press the play button in the upper right corner and see the nice debug output.
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2018-12-20 14:52:06 +01:00
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~~~rust
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use crate::chainerror::*;
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{{#include ../examples/tutorial2.rs:2:}}
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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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2018-12-20 15:14:21 +01:00
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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:11:13}}
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~~~
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The macro `cherr!(cause, newerror)` stores `cause` as the source/cause of `newerror` and returns
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`newerror`, along with the filename (`file!()`) and line number (`line!()`).
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`Err(e)?` then returns the error `e` applying `e.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>` is in our case `ChainError<String>`.
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