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<!DOCTYPE HTML>
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<title>Simple String Errors - chainerror</title>
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<meta name="description" content="A tutorial for the chainerror rust crate.">
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@ -30,11 +32,11 @@
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@ -75,7 +80,10 @@
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<nav id="sidebar" class="sidebar" aria-label="Table of contents">
<ol class="chapter"><li class="affix"><a href="index.html">chainerror</a></li><li><a href="tutorial1.html" class="active"><strong aria-hidden="true">1.</strong> Simple String Errors</a></li><li><a href="tutorial2.html"><strong aria-hidden="true">2.</strong> Simple Chained String Errors</a></li><li><a href="tutorial3.html"><strong aria-hidden="true">3.</strong> Mapping Errors</a></li><li><a href="tutorial4.html"><strong aria-hidden="true">4.</strong> Saving coding chars</a></li><li><a href="tutorial5.html"><strong aria-hidden="true">5.</strong> The source() of Errors</a></li><li><a href="tutorial6.html"><strong aria-hidden="true">6.</strong> Downcast the Errors</a></li><li><a href="tutorial7.html"><strong aria-hidden="true">7.</strong> The root cause of all Errors</a></li><li><a href="tutorial8.html"><strong aria-hidden="true">8.</strong> Finding an Error cause</a></li><li><a href="tutorial9.html"><strong aria-hidden="true">9.</strong> Selective Error Handling</a></li><li><a href="tutorial10.html"><strong aria-hidden="true">10.</strong> ErrorKind to the rescue</a></li><li><a href="tutorial11.html"><strong aria-hidden="true">11.</strong> Debug for the ErrorKind</a></li><li><a href="tutorial12.html"><strong aria-hidden="true">12.</strong> Deref for the ErrorKind</a></li><li><a href="tutorial13.html"><strong aria-hidden="true">13.</strong> Writing a library</a></li><li class="affix"><a href="end.html">The End</a></li></ol>
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<ol class="chapter"><li class="expanded affix "><a href="index.html">chainerror</a></li><li class="expanded "><a href="tutorial1.html" class="active"><strong aria-hidden="true">1.</strong> Simple String Errors</a></li><li class="expanded "><a href="tutorial2.html"><strong aria-hidden="true">2.</strong> Simple Chained String Errors</a></li><li class="expanded "><a href="tutorial3.html"><strong aria-hidden="true">3.</strong> Mapping Errors</a></li><li class="expanded "><a href="tutorial4.html"><strong aria-hidden="true">4.</strong> Saving coding chars</a></li><li class="expanded "><a href="tutorial5.html"><strong aria-hidden="true">5.</strong> The source() of Errors</a></li><li class="expanded "><a href="tutorial6.html"><strong aria-hidden="true">6.</strong> Downcast the Errors</a></li><li class="expanded "><a href="tutorial7.html"><strong aria-hidden="true">7.</strong> The root cause of all Errors</a></li><li class="expanded "><a href="tutorial8.html"><strong aria-hidden="true">8.</strong> Finding an Error cause</a></li><li class="expanded "><a href="tutorial9.html"><strong aria-hidden="true">9.</strong> Selective Error Handling</a></li><li class="expanded "><a href="tutorial10.html"><strong aria-hidden="true">10.</strong> ErrorKind to the rescue</a></li><li class="expanded "><a href="tutorial11.html"><strong aria-hidden="true">11.</strong> Debug for the ErrorKind</a></li><li class="expanded "><a href="tutorial12.html"><strong aria-hidden="true">12.</strong> Deref for the ErrorKind</a></li><li class="expanded "><a href="tutorial13.html"><strong aria-hidden="true">13.</strong> Writing a library</a></li><li class="expanded "><a href="tutorial14.html"><strong aria-hidden="true">14.</strong> Going back to std</a></li><li class="expanded affix "><a href="end.html">The End</a></li></ol>
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@ -105,7 +113,7 @@
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<h1 class="menu-title">chainerror</h1>
<h1 class="menu-title">chainerror</h1>
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@ -140,17 +148,17 @@
<div id="content" class="content">
<main>
<a class="header" href="#simple-string-errors" id="simple-string-errors"><h1>Simple String Errors</h1></a>
<h1><a class="header" href="#simple-string-errors" id="simple-string-errors">Simple String Errors</a></h1>
<p>An easy way of doing error handling in rust is by returning <code>String</code> as a <code>Box&lt;std::error::Error&gt;</code>.</p>
<p>If the rust <code>main</code> function returns an <code>Err()</code>, this <code>Err()</code> will be displayed with <code>std::fmt::Debug</code>.</p>
<p>As you can see by running the example (by pressing the &quot;Play&quot; button in upper right of the code block),
this only
<p>As you can see by running the example (by pressing the &quot;Play&quot; button in upper right of the code block),
this only
prints out the last <code>Error</code>.</p>
<pre><code>Error: StringError(&quot;func1 error&quot;)
</code></pre>
<p>The next chapters of this tutorial show how <code>chainerror</code> adds more information
and improves inspecting the sources of an error.</p>
<p>You can also run the tutorial examples in the checked out
<p>You can also run the tutorial examples in the checked out
<a href="https://github.com/haraldh/chainerror">chainerror git repo</a>.</p>
<pre><code>$ cargo run -q --example tutorial1
</code></pre>
@ -158,29 +166,28 @@ and improves inspecting the sources of an error.</p>
use std::io;
use std::result::Result;
fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
fn do_some_io() -&gt; Result&lt;(), Box&lt;Error + Send + Sync&gt;&gt; {
Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
fn func2() -&gt; Result&lt;(), Box&lt;Error + Send + Sync&gt;&gt; {
if let Err(_) = do_some_io() {
Err(&quot;func2 error&quot;)?;
}
Ok(())
}
fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
fn func1() -&gt; Result&lt;(), Box&lt;Error + Send + Sync&gt;&gt; {
if let Err(_) = func2() {
Err(&quot;func1 error&quot;)?;
}
Ok(())
}
fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
fn main() -&gt; Result&lt;(), Box&lt;Error + Send + Sync&gt;&gt; {
func1()
}
</code></pre></pre>
</main>
@ -225,6 +232,14 @@ fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
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