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<!-- Generated by pkgdown: do not edit by hand --><html lang="en"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta charset="utf-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Reactive domains — domains • shiny</title><!-- jquery --><script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.7.1/jquery.min.js" integrity="sha512-v2CJ7UaYy4JwqLDIrZUI/4hqeoQieOmAZNXBeQyjo21dadnwR+8ZaIJVT8EE2iyI61OV8e6M8PP2/4hpQINQ/g==" crossorigin="anonymous" referrerpolicy="no-referrer"></script><!-- Bootstrap --><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.4.1/css/bootstrap.min.css" integrity="sha256-bZLfwXAP04zRMK2BjiO8iu9pf4FbLqX6zitd+tIvLhE=" crossorigin="anonymous"><script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.4.1/js/bootstrap.min.js" integrity="sha256-nuL8/2cJ5NDSSwnKD8VqreErSWHtnEP9E7AySL+1ev4=" crossorigin="anonymous"></script><!-- bootstrap-toc --><link rel="stylesheet" href="../bootstrap-toc.css"><script src="../bootstrap-toc.js"></script><!-- Font Awesome icons --><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.12.1/css/all.min.css" integrity="sha256-mmgLkCYLUQbXn0B1SRqzHar6dCnv9oZFPEC1g1cwlkk=" crossorigin="anonymous"><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.12.1/css/v4-shims.min.css" integrity="sha256-wZjR52fzng1pJHwx4aV2AO3yyTOXrcDW7jBpJtTwVxw=" crossorigin="anonymous"><!-- clipboard.js --><script src="https://cdnjs.cloudflare.com/ajax/libs/clipboard.js/2.0.6/clipboard.min.js" integrity="sha256-inc5kl9MA1hkeYUt+EC3BhlIgyp/2jDIyBLS6k3UxPI=" crossorigin="anonymous"></script><!-- headroom.js --><script src="https://cdnjs.cloudflare.com/ajax/libs/headroom/0.11.0/headroom.min.js" integrity="sha256-AsUX4SJE1+yuDu5+mAVzJbuYNPHj/WroHuZ8Ir/CkE0=" crossorigin="anonymous"></script><script src="https://cdnjs.cloudflare.com/ajax/libs/headroom/0.11.0/jQuery.headroom.min.js" integrity="sha256-ZX/yNShbjqsohH1k95liqY9Gd8uOiE1S4vZc+9KQ1K4=" crossorigin="anonymous"></script><!-- pkgdown --><link href="../pkgdown.css" rel="stylesheet"><script src="../pkgdown.js"></script><meta property="og:title" content="Reactive domains — domains"><meta property="og:description" content="Reactive domains are a mechanism for establishing ownership over reactive
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<span class="version label label-default" data-toggle="tooltip" data-placement="bottom" title="">1.11.1.9000</span>
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</header><div class="row">
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<div class="col-md-9 contents">
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<div class="page-header">
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<h1>Reactive domains</h1>
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<small class="dont-index">Source: <a href="https://github.com/rstudio/shiny/blob/main/R/reactive-domains.R" class="external-link"><code>R/reactive-domains.R</code></a></small>
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<div class="hidden name"><code>domains.Rd</code></div>
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</div>
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<div class="ref-description">
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<p>Reactive domains are a mechanism for establishing ownership over reactive
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primitives (like reactive expressions and observers), even if the set of
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reactive primitives is dynamically created. This is useful for lifetime
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management (i.e. destroying observers when the Shiny session that created
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them ends) and error handling.</p>
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</div>
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<div id="ref-usage">
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<div class="sourceCode"><pre class="sourceCode r"><code><span><span class="fu">getDefaultReactiveDomain</span><span class="op">(</span><span class="op">)</span></span>
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<span></span>
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<span><span class="fu">withReactiveDomain</span><span class="op">(</span><span class="va">domain</span>, <span class="va">expr</span><span class="op">)</span></span>
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<span></span>
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<span><span class="fu">onReactiveDomainEnded</span><span class="op">(</span><span class="va">domain</span>, <span class="va">callback</span>, failIfNull <span class="op">=</span> <span class="cn">FALSE</span><span class="op">)</span></span></code></pre></div>
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</div>
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<div id="arguments">
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<h2>Arguments</h2>
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<dl><dt id="arg-domain">domain<a class="anchor" aria-label="anchor" href="#arg-domain"></a></dt>
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<dd><p>A valid domain object (for example, a Shiny session), or
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<code>NULL</code></p></dd>
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<dt id="arg-expr">expr<a class="anchor" aria-label="anchor" href="#arg-expr"></a></dt>
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<dd><p>An expression to evaluate under <code>domain</code></p></dd>
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<dt id="arg-callback">callback<a class="anchor" aria-label="anchor" href="#arg-callback"></a></dt>
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<dd><p>A callback function to be invoked</p></dd>
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<dt id="arg-failifnull">failIfNull<a class="anchor" aria-label="anchor" href="#arg-failifnull"></a></dt>
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<dd><p>If <code>TRUE</code> then an error is given if the <code>domain</code>
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is <code>NULL</code></p></dd>
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</dl></div>
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<div id="details">
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<h2>Details</h2>
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<p>At any given time, there can be either a single "default" reactive domain
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object, or none (i.e. the reactive domain object is <code>NULL</code>). You can
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access the current default reactive domain by calling
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<code>getDefaultReactiveDomain</code>.</p>
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<p>Unless you specify otherwise, newly created observers and reactive
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expressions will be assigned to the current default domain (if any). You can
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override this assignment by providing an explicit <code>domain</code> argument to
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<code><a href="reactive.html">reactive()</a></code> or <code><a href="observe.html">observe()</a></code>.</p>
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<p>For advanced usage, it's possible to override the default domain using
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<code>withReactiveDomain</code>. The <code>domain</code> argument will be made the
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default domain while <code>expr</code> is evaluated.</p>
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<p>Implementers of new reactive primitives can use <code>onReactiveDomainEnded</code>
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as a convenience function for registering callbacks. If the reactive domain
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is <code>NULL</code> and <code>failIfNull</code> is <code>FALSE</code>, then the callback will
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never be invoked.</p>
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</div>
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</div>
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<nav id="toc" data-toggle="toc" class="sticky-top"><h2 data-toc-skip>Contents</h2>
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<footer><div class="copyright">
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<p></p><p>Developed by Winston Chang, Joe Cheng, JJ Allaire, Carson Sievert, Barret Schloerke, Yihui Xie, Jeff Allen, Jonathan McPherson, Alan Dipert, Barbara Borges, Posit Software, PBC.</p>
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<p></p><p>Site built with <a href="https://pkgdown.r-lib.org/" class="external-link">pkgdown</a> 2.1.3.</p>
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