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<p class="MsoNormal"><span style="font-size:11.0pt">Hi list members,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">During code review today, I noticed a really subtle memory leak that looked like:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> self.relatedObject = RelatedObject(callback: relatedObjectDidFinish)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Where `relatedObject` is a strong reference, `callback` is an escaping closure, and `relatedObjectDidFinish` is a method of `self`. From a memory management perspective, this code is equivalent to:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> self.relatedObject = RelatedObject(callback: { self.relatedObjectDidFinish })<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">In the second example, an explicit `self.` is required. It’s my understanding that this is to highlight that the closure keeps a strong reference to `self`. But, when passing a method, there is no such requirement,
which makes it easier to accidentally create a retain cycle.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">This made me wonder if an explicit `self.` should be required when passing a method as an escaping closure. And whether that would help in the same way that the explicit `self.` *inside* the closure is intended
to.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">If it were required, the code in the first example would be:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> self.relatedObject = RelatedObject(callback: self.relatedObjectDidFinish)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">What do you think?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt">Alex Johnson<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><a href="mailto:ajohnson@walmartlabs.com"><span style="color:#0563C1">ajohnson@walmartlabs.com</span></a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">ajohnson on Slack</span><o:p></o:p></p>
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