StackOverflow2013

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copied!<blockquote> <p>But Objective-C objects still are more or less manually managed, and RAII idiom is entirely absent from the language.</p> </blockquote> <p>I think this would seem to answer your question anyhow. Because Objective-C objects are reference counted, they already fulfill the purpose smart pointers were created for: to divorce or tie the lifetime of an object from the scope of the method it's contained in. <code>scoped_ptr</code>s can be recreated with autorelease pools, and <code>shared_ptr</code>s with <code>-retain</code>-<code>-release</code> or <code>strong</code> references. </p> <p>But saying no is boring. If you really want to mingle Objective-C and C++ like this, we'll need to first loosen the definition of "Objective-C object". The runtime recognizes anything with an <code>isa</code> sitting as its first member as an object, and we can take advantage of that and write a simple C++ class with a corresponding object interface so it can be messaged:</p> <pre><code>@interface CFIObject : NSObject - (void)doSomething; @end struct CFIObject_cxx { Class isa; public: CFIObject_cxx() : isa([CFIObject class]) {} ~CFIObject_cxx() { printf("I'm dying!"); } }; @implementation CFIObject - (void)doSomething { NSLog("I did something."); } @end </code></pre> <p>We can now instantiate an instance of our C++ object and wrap it in a smart pointer, which I'm going to purposefully split into two methods to illustrate the lifetime of the object:</p> <pre><code>void func() { // Instantiate a smart pointer with our fake object. std::unique_ptr<CFIObject_cxx> cppObj (new CFIObject_cxx()); id obj = (__bridge id)(cppObj.get()); // The runtime thinks we're an object. [obj doSomething]; // aaaand, it's out of scope. } int main(int argc, const char **argv) { func(); return 0; } </code></pre> <p>As one would expect, this prints:</p> <pre><code>2013-12-22 17:23:22.681 Test[77528:303] I did something I'm dying! </code></pre> <p>to the console.</p> <p>If need be, the destructor could be outfitted to call through to <code>-dealloc</code> to simulate proper object destruction, but I hope you see that all of this is just wholly unnecessary, especially with ARC getting smarter with each release of CLANG.</p>

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