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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="API documentation for the Rust `log_enabled` macro in crate `log`."><meta name="keywords" content="rust, rustlang, rust-lang, log_enabled"><title>log::log_enabled - Rust</title><link rel="stylesheet" type="text/css" href="../normalize.css"><link rel="stylesheet" type="text/css" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><link rel="stylesheet" type="text/css" href="../dark.css" disabled ><link rel="stylesheet" type="text/css" href="../ayu.css" disabled ><script src="../storage.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="shortcut icon" href="https://www.rust-lang.org/favicon.ico"><style type="text/css">#crate-search{background-image:url("../down-arrow.svg");}</style></head><body class="rustdoc macro"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../log/index.html'><div class='logo-container'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo'></div></a><div class="sidebar-elems"><p class='location'><a href='index.html'>log</a></p><script>window.sidebarCurrent = {name: 'log_enabled', ty: 'macro', relpath: ''};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../theme.js"></script><nav class="sub"><form class="search-form"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" disabled autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><span class="help-button">?</span>
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<a id="settings-menu" href="../settings.html"><img src="../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='out-of-band'><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>−</span>]</a></span><a class='srclink' href='../src/log/macros.rs.html#210-220' title='goto source code'>[src]</a></span><span class='in-band'>Macro <a href='index.html'>log</a>::<wbr><a class="macro" href=''>log_enabled</a></span></h1><div class="docblock type-decl hidden-by-usual-hider"><div class="example-wrap"><pre class="rust macro">
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<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">log_enabled</span> {
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(<span class="ident">target</span>: <span class="macro-nonterminal">$</span><span class="macro-nonterminal">target</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">lvl</span>:<span class="ident">expr</span>) <span class="op">=></span> { ... };
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(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">lvl</span>:<span class="ident">expr</span>) <span class="op">=></span> { ... };
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}</pre></div>
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</div><div class='docblock'><p>Determines if a message logged at the specified level in that module will
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be logged.</p>
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<p>This can be used to avoid expensive computation of log message arguments if
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the message would be ignored anyway.</p>
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<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
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<div class='information'><div class='tooltip edition'>ⓘ<span class='tooltiptext'>This code runs with edition 2018</span></div></div><div class="example-wrap"><pre class="rust rust-example-rendered edition ">
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<span class="kw">use</span> <span class="ident">log</span>::<span class="ident">Level</span>::<span class="ident">Debug</span>;
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<span class="kw">use</span> <span class="ident">log</span>::{<span class="ident">debug</span>, <span class="ident">log_enabled</span>};
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<span class="kw">if</span> <span class="macro">log_enabled</span><span class="macro">!</span>(<span class="ident">Debug</span>) {
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<span class="kw">let</span> <span class="ident">data</span> <span class="op">=</span> <span class="ident">expensive_call</span>();
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<span class="macro">debug</span><span class="macro">!</span>(<span class="string">"expensive debug data: {} {}"</span>, <span class="ident">data</span>.<span class="ident">x</span>, <span class="ident">data</span>.<span class="ident">y</span>);
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}
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<span class="kw">if</span> <span class="macro">log_enabled</span><span class="macro">!</span>(<span class="ident">target</span>: <span class="string">"Global"</span>, <span class="ident">Debug</span>) {
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<span class="kw">let</span> <span class="ident">data</span> <span class="op">=</span> <span class="ident">expensive_call</span>();
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<span class="macro">debug</span><span class="macro">!</span>(<span class="ident">target</span>: <span class="string">"Global"</span>, <span class="string">"expensive debug data: {} {}"</span>, <span class="ident">data</span>.<span class="ident">x</span>, <span class="ident">data</span>.<span class="ident">y</span>);
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}</pre></div>
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