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<main><div class="width-limiter"><nav class="sub"><form class="search-form"><span></span><div id="sidebar-button" tabindex="-1"><a href="../strum/all.html" title="show sidebar"></a></div><input class="search-input" name="search" aria-label="Run search in the documentation" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" tabindex="-1"><a href="../help.html" title="help">?</a></div><div id="settings-menu" tabindex="-1"><a href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1>Derive Macro <a href="index.html">strum</a>::<wbr><a class="derive" href="#">EnumString</a><button id="copy-path" title="Copy item path to clipboard"><img src="../static.files/clipboard-7571035ce49a181d.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="src" href="../src/strum_macros/lib.rs.html#116">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>−</span>]</button></span></div><pre class="rust item-decl"><code>#[derive(EnumString)]
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{
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<span class="comment">// Attributes available to this derive:</span>
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#[strum]
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}
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</code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Converts strings to enum variants based on their name.</p>
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<p>auto-derives <code>std::str::FromStr</code> on the enum (for Rust 1.34 and above, <code>std::convert::TryFrom<&str></code>
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will be derived as well). Each variant of the enum will match on it’s own name.
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This can be overridden using <code>serialize="DifferentName"</code> or <code>to_string="DifferentName"</code>
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on the attribute as shown below.
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Multiple deserializations can be added to the same variant. If the variant contains additional data,
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they will be set to their default values upon deserialization.</p>
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<p>The <code>default</code> attribute can be applied to a tuple variant with a single data parameter. When a match isn’t
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found, the given variant will be returned and the input string will be captured in the parameter.</p>
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<p>Note that the implementation of <code>FromStr</code> by default only matches on the name of the
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variant. There is an option to match on different case conversions through the
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<code>#[strum(serialize_all = "snake_case")]</code> type attribute.</p>
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<p>See the <a href="https://docs.rs/strum/latest/strum/additional_attributes/index.html">Additional Attributes</a>
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Section for more information on using this feature.</p>
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<p>If you have a large enum, you may want to consider using the <code>use_phf</code> attribute here. It leverages
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perfect hash functions to parse much quicker than a standard <code>match</code>. (MSRV 1.46)</p>
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<h2 id="example-howto-use-enumstring"><a href="#example-howto-use-enumstring">Example howto use <code>EnumString</code></a></h2>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::str::FromStr;
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<span class="kw">use </span>strum_macros::EnumString;
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<span class="attr">#[derive(Debug, PartialEq, EnumString)]
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</span><span class="kw">enum </span>Color {
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Red,
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<span class="comment">// The Default value will be inserted into range if we match "Green".
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</span>Green {
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range: usize,
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},
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<span class="comment">// We can match on multiple different patterns.
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</span><span class="attr">#[strum(serialize = <span class="string">"blue"</span>, serialize = <span class="string">"b"</span>)]
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</span>Blue(usize),
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<span class="comment">// Notice that we can disable certain variants from being found
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</span><span class="attr">#[strum(disabled)]
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</span>Yellow,
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<span class="comment">// We can make the comparison case insensitive (however Unicode is not supported at the moment)
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</span><span class="attr">#[strum(ascii_case_insensitive)]
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</span>Black,
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}
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<span class="comment">/*
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//The generated code will look like:
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impl std::str::FromStr for Color {
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type Err = ::strum::ParseError;
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fn from_str(s: &str) -> ::core::result::Result<Color, Self::Err> {
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match s {
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"Red" => ::core::result::Result::Ok(Color::Red),
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"Green" => ::core::result::Result::Ok(Color::Green { range:Default::default() }),
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"blue" => ::core::result::Result::Ok(Color::Blue(Default::default())),
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"b" => ::core::result::Result::Ok(Color::Blue(Default::default())),
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s if s.eq_ignore_ascii_case("Black") => ::core::result::Result::Ok(Color::Black),
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_ => ::core::result::Result::Err(::strum::ParseError::VariantNotFound),
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}
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}
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}
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*/
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// simple from string
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</span><span class="kw">let </span>color_variant = Color::from_str(<span class="string">"Red"</span>).unwrap();
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<span class="macro">assert_eq!</span>(Color::Red, color_variant);
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<span class="comment">// short version works too
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</span><span class="kw">let </span>color_variant = Color::from_str(<span class="string">"b"</span>).unwrap();
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<span class="macro">assert_eq!</span>(Color::Blue(<span class="number">0</span>), color_variant);
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<span class="comment">// was disabled for parsing = returns parse-error
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</span><span class="kw">let </span>color_variant = Color::from_str(<span class="string">"Yellow"</span>);
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<span class="macro">assert!</span>(color_variant.is_err());
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<span class="comment">// however the variant is still normally usable
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</span><span class="macro">println!</span>(<span class="string">"{:?}"</span>, Color::Yellow);
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<span class="kw">let </span>color_variant = Color::from_str(<span class="string">"bLACk"</span>).unwrap();
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<span class="macro">assert_eq!</span>(Color::Black, color_variant);</code></pre></div>
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