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POobjective-c wrapper invoking c++ static member functions
 

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  1. POobjective-c wrapper invoking c++ static member functions
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    <p>I am trying to make an objective-c++ wrapper (.mm) between a pure c++ class (.cpp) and pure objective-c object (.m). A good working example can be <a href="https://github.com/boralben/ObjectiveCPPWrapperEx.git" rel="nofollow">found on github</a>. I can build and run this without a problem.</p> <p>However I need to access static member functions in the c++ class. I have modified the github example by removing all existing functions and introducing a static member function: </p> <pre><code>// ================== // DummyModel.h // ================== class DummyModel { public: static int test (); }; // ================== // DummyModel.cpp // ================== #include "DummyModel.h" static int test () { int x = 1; return x; } // ================== // DummyModelWrapper.h // ================== #import &lt;Foundation/Foundation.h&gt; @interface DummyModelWrapper : NSObject - (int) test; @end // ================== // DummyModelWrapper.mm // ================== #import "DummyModelWrapper.h" #import "DummyModel.h" @implementation DummyModelWrapper - (int) test { int result; result = DummyModel::test(); return result; } @end </code></pre> <p>This yields the following error:</p> <pre><code>Undefined symbols for architecture i386: "DummyModel::test()", referenced from: -[DummyModelWrapper test] in DummyModelWrapper.o ld: symbol(s) not found for architecture i386 clang: error: linker command failed with exit code 1 (use -v to see invocation) </code></pre> <p>It is this reference to test in DummyModelWrapper.mm that is invoking the error: </p> <pre><code> result = DummyModel::test(); </code></pre> <p>The test project is adapted from the github project, which compiles and runs fine in it's unedited form (it instantiates <code>DummyModel</code> and invokes member functions on the instance). The error occurs as soon as I attempt to add a static member and access it from the wrapper object.</p> <p>I have read everything i can find on stackoverflow and elsewhere, but can only find examples involving non-static member functions. </p> <p><em>references</em><br> <a href="http://www.philjordan.eu/article/mixing-objective-c-c++-and-objective-c++" rel="nofollow">http://www.philjordan.eu/article/mixing-objective-c-c++-and-objective-c++</a><br> <a href="http://robnapier.net/blog/wrapping-cppfinal-edition-759" rel="nofollow">http://robnapier.net/blog/wrapping-cppfinal-edition-759</a><br> <a href="http://www.boralapps.com/an-objective-c-project-that-uses-c/294/" rel="nofollow">http://www.boralapps.com/an-objective-c-project-that-uses-c/294/</a> </p> <p><em>environment</em><br> xcode 4.5.2/osx8.2 (targeting ios5+)</p>
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    1. COIf you're invoking C++ code in that ".m" file, shouldn't it be a ".mm" file extension instead? Or perhaps the comment in the source file is inaccurate? Regardless, see [benjorbin's](http://stackoverflow.com/questions/14104510/objective-c-wrapper-invoking-c-static-member-functions/14104585#14104585) answer below.
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    2. COyes, sorry that was a bad typo, fixed in the question
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