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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Serialize with an added prefix on every field name and deserialize by trimming away the prefix."><title>with_prefix in serde_with - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><link rel="stylesheet" href="../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../static.files/rustdoc-ac92e1bbe349e143.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="serde_with" data-themes="" data-resource-suffix="" data-rustdoc-version="1.76.0 (07dca489a 2024-02-04)" data-channel="1.76.0" data-search-js="search-2b6ce74ff89ae146.js" data-settings-js="settings-4313503d2e1961c2.js" ><script src="../static.files/storage-f2adc0d6ca4d09fb.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-305769736d49e732.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-feafe1bb7466e4bd.css"></noscript><link rel="alternate icon" type="image/png" href="../static.files/favicon-16x16-8b506e7a72182f1c.png"><link rel="alternate icon" type="image/png" href="../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc macro"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">☰</button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../serde_with/index.html">serde_with</a><span class="version">2.3.3</span></h2></div><div class="sidebar-elems"></div></nav><div class="sidebar-resizer"></div>
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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="../serde_with/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>Macro <a href="index.html">serde_with</a>::<wbr><a class="macro" href="#">with_prefix</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/serde_with/with_prefix.rs.html#104-136">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>−</span>]</button></span></div><pre class="rust item-decl"><span class="macro">macro_rules! </span>with_prefix {
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(<span class="macro-nonterminal">$module</span>:ident <span class="macro-nonterminal">$prefix</span>:expr) => { ... };
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(<span class="macro-nonterminal">$vis</span>:vis <span class="macro-nonterminal">$module</span>:ident <span class="macro-nonterminal">$prefix</span>:expr) => { ... };
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}</pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Serialize with an added prefix on every field name and deserialize by
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trimming away the prefix.</p>
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<p>You can set the visibility of the generated module by prefixing the module name with a module visibility.
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<code>with_prefix!(pub(crate) prefix_foo "foo_");</code> creates a module with <code>pub(crate)</code> visibility.
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The visibility is optional and by default <code>pub(self)</code>, i.e., private visibility is assumed.</p>
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<p><strong>Note:</strong> Use of this macro is incompatible with applying the <a href="https://serde.rs/container-attrs.html#deny_unknown_fields"><code>deny_unknown_fields</code></a> attribute
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on the container.
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While deserializing, it will always warn about unknown fields, even though they are processed
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by the <code>with_prefix</code> wrapper.
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More details can be found in <a href="https://github.com/jonasbb/serde_with/issues/57">this issue</a>.</p>
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<h2 id="example"><a href="#example">Example</a></h2>
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<p>The <a href="https://api.challonge.com/v1/documents/matches/show">Challonge REST API</a> likes to use prefixes to group related fields. In
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simplified form, their JSON may resemble the following:</p>
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<div class="example-wrap"><pre class="language-json"><code>{
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"player1_name": "name1",
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"player1_votes": 1,
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"player2_name": "name2",
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"player2_votes": 2
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}
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</code></pre></div>
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<p>In Rust, we would ideally like to model this data as a pair of <code>Player</code>
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structs, rather than repeating the fields of <code>Player</code> for each prefix.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">struct </span>Match {
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player1: Player,
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player2: Player,
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}
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<span class="kw">struct </span>Player {
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name: String,
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votes: u64,
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}</code></pre></div>
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<p>This <code>with_prefix!</code> macro produces an adapter that adds a prefix onto field
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names during serialization and trims away the prefix during deserialization.
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An implementation of the Challonge API would use <code>with_prefix!</code> like this:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>serde::{Deserialize, Serialize};
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<span class="kw">use </span>serde_with::with_prefix;
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<span class="attr">#[derive(Serialize, Deserialize)]
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</span><span class="kw">struct </span>Match {
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<span class="attr">#[serde(flatten, with = <span class="string">"prefix_player1"</span>)]
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</span>player1: Player,
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<span class="attr">#[serde(flatten, with = <span class="string">"prefix_player2"</span>)]
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</span>player2: Player,
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}
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<span class="attr">#[derive(Serialize, Deserialize)]
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</span><span class="kw">struct </span>Player {
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name: String,
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votes: u64,
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}
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<span class="macro">with_prefix!</span>(prefix_player1 <span class="string">"player1_"</span>);
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<span class="comment">// You can also set the visibility of the generated prefix module, the default is private.
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</span><span class="macro">with_prefix!</span>(<span class="kw">pub </span>prefix_player2 <span class="string">"player2_"</span>);
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<span class="kw">fn </span>main() {
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<span class="kw">let </span>m = Match {
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player1: Player {
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name: <span class="string">"name1"</span>.to_owned(),
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votes: <span class="number">1</span>,
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},
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player2: Player {
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name: <span class="string">"name2"</span>.to_owned(),
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votes: <span class="number">2</span>,
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},
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};
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<span class="kw">let </span>j = serde_json::to_string_pretty(<span class="kw-2">&</span>m).unwrap();
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<span class="macro">println!</span>(<span class="string">"{}"</span>, j);
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}</code></pre></div>
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</div></details></section></div></main></body></html> |