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<h1 class="title">Borrow and AsRef</h1>
<p><small>There is a new edition of the book and this is an old link.</small></p>
<blockquote>
<p>A cheap reference-to-reference conversion.
Used to convert a value to a reference value within generic code.</p>
</blockquote>
<pre class="rust rust-example-rendered">
<span class="kw">fn</span> <span class="ident">is_hello</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">AsRef</span><span class="op"><</span><span class="ident">str</span><span class="op">>></span>(<span class="ident">s</span>: <span class="ident">T</span>) {
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="string">"hello"</span>, <span class="ident">s</span>.<span class="ident">as_ref</span>());
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Afn%20is_hello%3CT%3A%20AsRef%3Cstr%3E%3E(s%3A%20T)%20%7B%0A%20%20%20assert_eq!(%22hello%22%2C%20s.as_ref())%3B%0A%7D%0A%7D">Run</a></pre>
<hr />
<p>This chapter does not exist in <a href="second-edition/index.html">the second edition</a>.
The best place to learn more about this is <a href="../std/convert/trait.AsRef.html">the Rust documentation</a>.</p>
<ul>
<li><strong><a href="../std/convert/trait.AsRef.html">In the Rust documentation: <code>convert::AsRef</code></a></strong></li>
<li><small><a href="first-edition/borrow-and-asref.html">In the first edition: Ch 4.10 — Borrow and AsRef</a></small></li>
</ul>
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