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POiOS Memory Management followup. dealloc vs nil?
 

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    <p>With regards to this posting: <a href="https://stackoverflow.com/questions/1458178/iphone-dealloc-release-vs-nil">iPhone - dealloc - Release vs. nil</a></p> <pre><code>1) [foo release]; 2) self.bar = nil; </code></pre> <p>The explanation was as follows:</p> <ol> <li><p>Is releasing the object, accessing it through the instance variable <em>bar</em>. The instance variable will become a dangling pointer. This is the preferred method in dealloc.</p></li> <li><p>Is assigning nil to a property bar on self, that will in practice release whatever the property is currently retaining. Do this if you have a custom setter for the property, that is supposed to cleanup more than just the instance variable backing the property.</p></li> </ol> <p>Could someone please clarify the explanation for #1? Accessed through the instance variable <em>bar</em> ?</p> <p>E.g I have set a private var in my object header as so:</p> <pre><code>SomeObject *oPointer; </code></pre> <p>I am not using a property setter with this pointer in the header file and it does <strong>NOT</strong> get synthesized when instantiate the object.</p> <p>In my code, given certain conditions, I later have to allocate and assign this pointer to it's object.</p> <pre><code>obj = [[SomeObject alloc] initWith....]; </code></pre> <p>So this is now accessed through the instance variable <em>obj</em>. I have a UIButton which is configured to RESET this object it's attached method deallocs it. I do this via:</p> <pre><code>[obj release]; obj = nil; </code></pre> <p>After all that explaining the question is, why do I also <strong>have</strong> to declare the obj = nil? The <em>[obj release]</em> call seems to also kill the pointer. I was thinking that <em>[obj release]</em> would deallocate the memory it's pointing to and also set <em>obj</em> to nil all in one shot but it seems it also kills the pointer because my app crashes when it tries to reference <em>obj</em> after <em>[obj release]</em>;</p> <p>Does this question make sense? Is the explanation simply that <em>[obj release]</em> does <em>ALL</em> cleanup, including killing the pointer and I need to be aware of that? </p> <p>If I set a retain property for the SomeObject pointer would the pointer still be retained after release? </p> <p>Thanks in advance!</p>
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