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Edit File: faq-adverbs-export.html

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<table width="100%" summary="page for faq-adverbs-export {purrr}"><tr><td>faq-adverbs-export {purrr}</td><td style="text-align: right;">R Documentation</td></tr></table>

<h2>Best practices for exporting adverb-wrapped functions</h2>

<h3>Description</h3>

<p>Functions like <code><a href="insistently.html">insistently()</a></code>, <code><a href="safely.html">safely()</a></code>, <code><a href="insistently.html">slowly()</a></code>, and
<code><a href="safely.html">quietly()</a></code> help resolve challenging issues in programming. For
example, <code><a href="safely.html">safely()</a></code> modifies a function to return both an error and
a result. These functions work by returning an enhanced version of
the original function. They are often called <strong>adverb</strong> functions
and are typically named with an informative prefix such as <code>safe_</code>
or <code>insist_.</code> For instance, an insistent variant of <code>scrape_data()</code>
created with <code>insistently()</code> might be called <code>insist_scrape_data()</code>.
</p>
<p>Exporting functions created with purrr adverbs in your package
requires some precautions. Because the functions created by adverbs
contain internal purrr code, creating them once and for all when
the package is built might cause problems when purrr is
updated. Instead, the function must be created by the purrr adverb
each time the package is loaded in memory via the <code><a href="../../base/html/ns-hooks.html">.onLoad()</a></code> hook
of the package. This prevents the generated functions to contain
outdated internal purrr code (which could even refer to functions
that no longer exist in the purrr namespace).
</p>
<p>An example if provided below for <code>insist</code>, but it would be very
similar for functions generated by other adverbs.</p>
<pre>#' My function
insist_my_function &lt;- function(...) "dummy"

my_function &lt;- function(...) {
  # Implementation
}

.onLoad &lt;- function(lib, pkg) {
  insist_my_function &lt;&lt;- purrr::insistently(my_function)
}
</pre>

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