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POPassing a C++ method to an Objective-C method
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copied!<p>I have a C++ class '<code>Expression</code>' with a method I'd like to use in my Objective-C class '<code>GraphVC</code>'.</p> <pre><code>class Expression { double evaluate(double); } </code></pre> <p>And my Objective-C class:</p> <pre><code>@implementation GraphVC : UIViewController { - (void)plot:(double(*)(double))f; @end </code></pre> <p>I thought that it would be easiest to pass around function pointers that take a double and return a double, as opposed to C++ objects, but I haven't had much success using <code>functional.h</code>. What's the best way to use my C++ method from Objective-C?</p> <p>EDIT: Thanks for your quick responses. Allow me to elaborate a bit... I have a backend written in C++ where I manipulate objects of type Expression. There's subclasses for rational, polynomial, monomial, etc. My initial idea was to use <a href="http://www.cplusplus.com/reference/std/functional/mem_fun/" rel="nofollow noreferrer">mem_fun</a> from , but I wasn't able to get code compiling this way. I also had trouble using bind1st to bind the <code>this</code> pointer.</p> <ul> <li>Writing an Objective-C wrapper is a possibility, but I'd rather use the already existing <code>evaluate()</code> function, and I don't want to break the clean separation between the backend and the iPhone GUI classes.</li> <li>I can't have a global expression or use a static method (I need to plot arbitrary <code>Expression</code> instances.</li> </ul> <p>I should have more explicitly stated that I need to pass a C++ member function (not a static function or existing C function) to an Objective-C object. Has anyone had luck using C++'s <code><functional></code> to turn member functions into pointers I can use in an Objective-C object, or should I use an Objective-C wrapper? </p>

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