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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>Create a non-reactive scope for an expression — isolate • 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="Create a non-reactive scope for an expression — isolate"><meta property="og:description" content="Executes the given expression in a scope where reactive values or expression
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<h1>Create a non-reactive scope for an expression</h1>
<small class="dont-index">Source: <a href="https://github.com/rstudio/shiny/blob/rc-v1.12.1/R/reactives.R" class="external-link"><code>R/reactives.R</code></a></small>
<div class="hidden name"><code>isolate.Rd</code></div>
</div>
<div class="ref-description">
<p>Executes the given expression in a scope where reactive values or expression
can be read, but they cannot cause the reactive scope of the caller to be
re-evaluated when they change.</p>
</div>
<div id="ref-usage">
<div class="sourceCode"><pre class="sourceCode r"><code><span><span class="fu">isolate</span><span class="op">(</span><span class="va">expr</span><span class="op">)</span></span></code></pre></div>
</div>
<div id="arguments">
<h2>Arguments</h2>
<dl><dt id="arg-expr">expr<a class="anchor" aria-label="anchor" href="#arg-expr"></a></dt>
<dd><p>An expression that can access reactive values or expressions.</p></dd>
</dl></div>
<div id="details">
<h2>Details</h2>
<p>Ordinarily, the simple act of reading a reactive value causes a relationship
to be established between the caller and the reactive value, where a change
to the reactive value will cause the caller to re-execute. (The same applies
for the act of getting a reactive expression's value.) The <code>isolate</code>
function lets you read a reactive value or expression without establishing this
relationship.</p>
<p>The expression given to <code>isolate()</code> is evaluated in the calling
environment. This means that if you assign a variable inside the
<code>isolate()</code>, its value will be visible outside of the <code>isolate()</code>.
If you want to avoid this, you can use <code><a href="https://rdrr.io/r/base/eval.html" class="external-link">base::local()</a></code> inside the
<code>isolate()</code>.</p>
<p>This function can also be useful for calling reactive expression at the
console, which can be useful for debugging. To do so, simply wrap the
calls to the reactive expression with <code>isolate()</code>.</p>
</div>
<div id="ref-examples">
<h2>Examples</h2>
<div class="sourceCode"><pre class="sourceCode r"><code><span class="r-in"><span><span class="kw">if</span> <span class="op">(</span><span class="cn">FALSE</span><span class="op">)</span> <span class="op">{</span> <span class="co"># \dontrun{</span></span></span>
<span class="r-in"><span><span class="fu"><a href="observe.html">observe</a></span><span class="op">(</span><span class="op">{</span></span></span>
<span class="r-in"><span> <span class="va">input</span><span class="op">$</span><span class="va">saveButton</span> <span class="co"># Do take a dependency on input$saveButton</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span> <span class="co"># isolate a simple expression</span></span></span>
<span class="r-in"><span> <span class="va">data</span> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io/r/base/get.html" class="external-link">get</a></span><span class="op">(</span><span class="fu">isolate</span><span class="op">(</span><span class="va">input</span><span class="op">$</span><span class="va">dataset</span><span class="op">)</span><span class="op">)</span> <span class="co"># No dependency on input$dataset</span></span></span>
<span class="r-in"><span> <span class="fu">writeToDatabase</span><span class="op">(</span><span class="va">data</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="op">}</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span><span class="fu"><a href="observe.html">observe</a></span><span class="op">(</span><span class="op">{</span></span></span>
<span class="r-in"><span> <span class="va">input</span><span class="op">$</span><span class="va">saveButton</span> <span class="co"># Do take a dependency on input$saveButton</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span> <span class="co"># isolate a whole block</span></span></span>
<span class="r-in"><span> <span class="va">data</span> <span class="op">&lt;-</span> <span class="fu">isolate</span><span class="op">(</span><span class="op">{</span></span></span>
<span class="r-in"><span> <span class="va">a</span> <span class="op">&lt;-</span> <span class="va">input</span><span class="op">$</span><span class="va">valueA</span> <span class="co"># No dependency on input$valueA or input$valueB</span></span></span>
<span class="r-in"><span> <span class="va">b</span> <span class="op">&lt;-</span> <span class="va">input</span><span class="op">$</span><span class="va">valueB</span></span></span>
<span class="r-in"><span> <span class="fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span>a<span class="op">=</span><span class="va">a</span>, b<span class="op">=</span><span class="va">b</span><span class="op">)</span></span></span>
<span class="r-in"><span> <span class="op">}</span><span class="op">)</span></span></span>
<span class="r-in"><span> <span class="fu">writeToDatabase</span><span class="op">(</span><span class="va">data</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="op">}</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span><span class="fu"><a href="observe.html">observe</a></span><span class="op">(</span><span class="op">{</span></span></span>
<span class="r-in"><span> <span class="va">x</span> <span class="op">&lt;-</span> <span class="fl">1</span></span></span>
<span class="r-in"><span> <span class="co"># x outside of isolate() is affected</span></span></span>
<span class="r-in"><span> <span class="fu">isolate</span><span class="op">(</span><span class="va">x</span> <span class="op">&lt;-</span> <span class="fl">2</span><span class="op">)</span></span></span>
<span class="r-in"><span> <span class="fu"><a href="https://rdrr.io/r/base/print.html" class="external-link">print</a></span><span class="op">(</span><span class="va">x</span><span class="op">)</span> <span class="co"># 2</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span> <span class="va">y</span> <span class="op">&lt;-</span> <span class="fl">1</span></span></span>
<span class="r-in"><span> <span class="co"># Use local() to avoid affecting calling environment</span></span></span>
<span class="r-in"><span> <span class="fu">isolate</span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/eval.html" class="external-link">local</a></span><span class="op">(</span><span class="va">y</span> <span class="op">&lt;-</span> <span class="fl">2</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-in"><span> <span class="fu"><a href="https://rdrr.io/r/base/print.html" class="external-link">print</a></span><span class="op">(</span><span class="va">y</span><span class="op">)</span> <span class="co"># 1</span></span></span>
<span class="r-in"><span><span class="op">}</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span><span class="op">}</span> <span class="co"># }</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span><span class="co"># Can also use isolate to call reactive expressions from the R console</span></span></span>
<span class="r-in"><span><span class="va">values</span> <span class="op">&lt;-</span> <span class="fu"><a href="reactiveValues.html">reactiveValues</a></span><span class="op">(</span>A<span class="op">=</span><span class="fl">1</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="va">fun</span> <span class="op">&lt;-</span> <span class="fu"><a href="reactive.html">reactive</a></span><span class="op">(</span><span class="op">{</span> <span class="fu"><a href="https://rdrr.io/r/base/character.html" class="external-link">as.character</a></span><span class="op">(</span><span class="va">values</span><span class="op">$</span><span class="va">A</span><span class="op">)</span> <span class="op">}</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="fu">isolate</span><span class="op">(</span><span class="fu">fun</span><span class="op">(</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-out co"><span class="r-pr">#&gt;</span> [1] "1"</span>
<span class="r-in"><span><span class="co"># "1"</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span><span class="co"># isolate also works if the reactive expression accesses values from the</span></span></span>
<span class="r-in"><span><span class="co"># input object, like input$x</span></span></span>
</code></pre></div>
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