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<h4>Nat!</h4>
<p>Senior Mull</p>
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<article>
<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/intro.html" title="De Re mulle-objc">De Re mulle-objc</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/modern.html" title="Project Setup">Project Setup</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/pnp-dependency.html" title="Dependencies">Dependencies</a>
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<article>
<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/modern-complex.html" title="Projects with Multiple Targets">Projects with Multiple Targets</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/good.html" title="Good mulle-objc Code">Good mulle-objc Code</a>
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<article>
<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/basics.html" title="A complete class">A complete class</a>
</article>
<article>
<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/objects.html" title="Objects and Properties">Objects and Properties</a>
</article>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/printing.html" title="Printing">Printing</a>
</article>
<article>
<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/pnp-class.html" title="Plug And Play Class">Plug And Play Class</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/pnp-category.html" title="Plug And Play Category">Plug And Play Category</a>
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<article>
<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/overridden.html" title="Advanced: Calling overridden methods">Advanced: Calling overridden methods</a>
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</article>
<article>
<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/protocolclass.html" title="Advanced: Protocolclasses allow default implementations">Advanced: Protocolclasses allow default implementations</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/classcluster.html" title="Advanced: Classcluster Classes">Advanced: Classcluster Classes</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/singleton.html" title="Advanced: Singleton classes">Advanced: Singleton classes</a>
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<article>
<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/tps.html" title="Advanced: Tagged Pointer Classes">Advanced: Tagged Pointer Classes</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/differences.html" title="Porting: Differences to Objective-C 2.0">Porting: Differences to Objective-C 2.0</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/porting.html" title="Porting: General Tips">Porting: General Tips</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/subscripting.html" title="Porting: subscripting">Porting: subscripting</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/arc.html" title="Porting: ARC">Porting: ARC</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/block.html" title="Porting: ^blocks">Porting: ^blocks</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/dotsyntax.html" title="Porting: . syntax for properties">Porting: . syntax for properties</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/protocol.html" title="Porting: Protocols are a kind of @selector">Porting: Protocols are a kind of @selector</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/property.html" title="Porting @property">Porting @property</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/synthesize.html" title="Porting: @synthesize is useless now">Porting: @synthesize is useless now</a>
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<li class="no-bullet"><a class="internal-link" href="/de-re-mulle-objc/reduction.html" title="Tooling: Code reduction">Tooling: Code reduction</a>
</article>
</ul>
<h5> Or read it like a <a href="book.html"><b>book</b></a>.</h6>
</div> <!-- contents -->
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</div>
<div id="post-second" class="eight columns">
<div class="title">
<div>
<h2>De Re mulle-objc <div style="font-size:10px; display: inline-block;">0.50.0</div> <a href="feed.xml"><img class="inline-img" src='images/feed-icon-28x28.png'></a></h2>
</div>
<h6>© 2025 by Nat!, Mulle kybernetiK. All rights reserved.</h6>
<p>
</div> <!-- title -->
<p>
<div id="main" role="main">
<article>
<h1>Porting @property</h1>
<div>
<p>Porting properties in a fashion that works in ARC code and in mulle-objc is
tricky. It is best if you can restrict yourself to <strong>assign</strong>, <strong>copy</strong> and <strong>retain</strong>.</p>
<h2 id="property-deallocation">Property deallocation</h2>
<div class="alert alert-info" role="alert"><i class="fa fa-info-circle"></i> <b>Note:</b> This is a rare case, where mulle-objc is compatible with ARC, but incompatible with MMR.</div>
<p>In Apple ARC, properties are automatically cleared during <code class="language-plaintext highlighter-rouge">-dealloc</code>. In Apple Manual Retain-Release Mode (MRR)
you have to do it yourself during <code class="language-plaintext highlighter-rouge">-dealloc</code>.</p>
<p>In mulle-objc all properties that reference objects or pointers are cleared during <code class="language-plaintext highlighter-rouge">-finalize</code> by
setting them to <strong>0</strong>.</p>
<p><strong>readonly</strong> properties - they have no setter - are not cleared. But in mulle-objc <em>they are backed by an <strong>ivar</strong></em>.
It is open to discussion if you want to release them in <code class="language-plaintext highlighter-rouge">-dealloc</code> for compatibility or use <code class="language-plaintext highlighter-rouge">-finalize</code> to break
possible retain cycles.</p>
<p>Here is how to write <code class="language-plaintext highlighter-rouge">-dealloc</code> for compatiblity with MMR (also see <a href="arc.html">ARC Porting tips</a>):</p>
<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>#if __has_feature(objc_arc) || defined( __MULLE_OBJC__)
# define PROPERTY_RELEASE( p)
#else
# define PROPERTY_RELEASE( p) [_p release]
#endif
#if __has_feature(objc_arc)
# define SUPER_DEALLOC()
#else
# define SUPER_DEALLOC( p) [super dealloc]
#endif
- (void) dealloc
{
PROPERTY_RELEASE( a)
PROPERTY_RELEASE( b)
PROPERTY_RELEASE( c)
SUPER_DEALLOC()
}
</code></pre></div></div>
<h2 id="missing-attributes">Missing Attributes</h2>
<h3 id="atomic">atomic</h3>
<p>Yup it’s gone. Use locking or the atomic operations provided by
<a href="//github.com/mulle-concurrent/mulle-thread">mulle-thread</a>.</p>
<h3 id="weak">weak</h3>
<p>Use <strong>assign</strong> instead.</p>
<div class="alert alert-info" role="alert"><i class="fa fa-info-circle"></i> <b>Note:</b> Use C containers to manage weak references
instead. They won’t <em>magically</em> cleanup though.</div>
<h3 id="strong">strong</h3>
<p>When declaring a property use <strong>copy</strong> or <strong>retain</strong>. You usually
use <strong>copy</strong> for <code class="language-plaintext highlighter-rouge">NSValue</code>, <code class="language-plaintext highlighter-rouge">NSDate</code>, <code class="language-plaintext highlighter-rouge">NSNumber</code> and <code class="language-plaintext highlighter-rouge">NSString</code> arguments,
and <strong>retain</strong> for everything else.</p>
<h3 id="nullable">nullable</h3>
<p>One of the strong points of Objective-C is its gracious handling of
<code class="language-plaintext highlighter-rouge">nil</code> values, which simplifies coding a lot. Remember that messaging <code class="language-plaintext highlighter-rouge">nil</code>
also produces <code class="language-plaintext highlighter-rouge">nil</code>. With the introduction of <code class="language-plaintext highlighter-rouge">nonnull</code> <code class="language-plaintext highlighter-rouge">nullable</code> was
also introduced. It is superflous.</p>
<p>You can easily get rid of <code class="language-plaintext highlighter-rouge">nullable</code> compile errors with:</p>
<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>#define nullable
</code></pre></div></div>
<div class="alert alert-info" role="alert"><i class="fa fa-info-circle"></i> <b>Note:</b> Tedious checks for <code class="language-plaintext highlighter-rouge">nil</code> means you are optimizing
your code for the error case. Use <strong>nonnull</strong> sparingly. If a <code class="language-plaintext highlighter-rouge">nil</code> parameter
has no ill effect, don’t mark the code <strong>nonnull</strong>.</div>
<h3 id="unsafe_unretained">unsafe_unretained</h3>
<p>Use <strong>assign</strong> instead.</p>
<h3 id="class">class</h3>
<p>Remove the property. Use <code class="language-plaintext highlighter-rouge">static</code> variables in your <code class="language-plaintext highlighter-rouge">@implementation</code>
then write and declare <code class="language-plaintext highlighter-rouge">+</code> accessors for them.</p>
<div class="alert alert-info" role="alert"><i class="fa fa-info-circle"></i> <b>Note:</b> <code class="language-plaintext highlighter-rouge">class</code> is likely to make a comeback in a future version.</div>
</div>
</article>
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navigator.clipboard.writeText(code.textContent).then(() => {
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const originalHTML = button.innerHTML;
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// Reset after delay
setTimeout(() => {
// Restore original icon
button.innerHTML = originalHTML;
// fidget this for reasons...
button.style.color = '#6a6a7c';
}, 500);
});
});
});
</script>
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_paq.push(['trackPageView']);
_paq.push(['enableLinkTracking']);
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var u="//www.mulle-kybernetik.com/matomo/";
_paq.push(['setTrackerUrl', u+'matomo.php']);
_paq.push(['setSiteId', '1']);
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