| <!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="Downcast an `Array` to a `RunArray` based on its `DataType`, accepts a number of subsequent patterns to match the data type"><title>downcast_run_array in arrow_array - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Italic-81dc35de.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-MediumItalic-ccf7e434.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2"href="../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../static.files/rustdoc-ca0dd0c4.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="arrow_array" data-themes="" data-resource-suffix="" data-rustdoc-version="1.92.0-nightly (53a741fc4 2025-10-16)" data-channel="nightly" data-search-js="search-8d3311b9.js" data-stringdex-js="stringdex-828709d0.js" data-settings-js="settings-c38705f0.js" ><script src="../static.files/storage-e2aeef58.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-ce535bd0.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-263c88ec.css"></noscript><link rel="icon" href="https://arrow.apache.org/img/arrow-logo_chevrons_black-txt_transparent-bg.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]--><rustdoc-topbar><h2><a href="#">downcast_run_array</a></h2></rustdoc-topbar><nav class="sidebar"><div class="sidebar-crate"><a class="logo-container" href="../arrow_array/index.html"><img src="https://arrow.apache.org/img/arrow-logo_chevrons_black-txt_white-bg.svg" alt="logo"></a><h2><a href="../arrow_array/index.html">arrow_<wbr>array</a><span class="version">56.2.0</span></h2></div><div class="sidebar-elems"><div id="rustdoc-modnav"></div></div></nav><div class="sidebar-resizer" title="Drag to resize sidebar"></div><main><div class="width-limiter"><section id="main-content" class="content"><div class="main-heading"><div class="rustdoc-breadcrumbs"><a href="index.html">arrow_array</a></div><h1>Macro <span class="macro">downcast_<wbr>run_<wbr>array</span> <button id="copy-path" title="Copy item path to clipboard">Copy item path</button></h1><rustdoc-toolbar></rustdoc-toolbar><span class="sub-heading"><a class="src" href="../src/arrow_array/cast.rs.html#656-672">Source</a> </span></div><pre class="rust item-decl"><code>macro_rules! downcast_run_array { |
| ($values:ident => $e:expr, $($p:pat $(if $pred:expr)* => $fallback:expr $(,)*)*) => { ... }; |
| ($values:ident => $e:block $($p:pat $(if $pred:expr)* => $fallback:expr $(,)*)*) => { ... }; |
| }</code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Downcast an <a href="array/trait.Array.html" title="trait arrow_array::array::Array"><code>Array</code></a> to a <a href="array/struct.RunArray.html" title="struct arrow_array::array::RunArray"><code>RunArray</code></a> based on its <a href="arrow_schema::DataType"><code>DataType</code></a>, accepts |
| a number of subsequent patterns to match the data type</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code> |
| <span class="kw">fn </span>print_strings(array: <span class="kw-2">&</span><span class="kw">dyn </span>Array) { |
| <span class="macro">downcast_run_array!</span>( |
| array => <span class="kw">match </span>array.values().data_type() { |
| DataType::Utf8 => { |
| <span class="kw">for </span>v <span class="kw">in </span>array.downcast::<StringArray>().unwrap() { |
| <span class="macro">println!</span>(<span class="string">"{:?}"</span>, v); |
| } |
| } |
| t => <span class="macro">println!</span>(<span class="string">"Unsupported run array value type {}"</span>, t), |
| }, |
| DataType::Utf8 => { |
| <span class="kw">for </span>v <span class="kw">in </span>as_string_array(array) { |
| <span class="macro">println!</span>(<span class="string">"{:?}"</span>, v); |
| } |
| } |
| <span class="comment">// You can also add a guard to the pattern |
| </span>DataType::LargeUtf8 <span class="kw">if </span><span class="bool-val">true </span>=> { |
| <span class="kw">for </span>v <span class="kw">in </span>as_largestring_array(array) { |
| <span class="macro">println!</span>(<span class="string">"{:?}"</span>, v); |
| } |
| } |
| t => <span class="macro">println!</span>(<span class="string">"Unsupported datatype {}"</span>, t) |
| ) |
| }</code></pre></div></div></details></section></div></main></body></html> |
