easing c++ to objective-c/cocoa bridging via metaprogramming?

Question

I didn’t find anything satisfactory and came up with a prototype that, given the following informal protocol:

- (NSString*)concatString:(NSString*)s1 withString:(NSString*)s2;

and this C++ code:

struct CppClass {
    std::string concatStrings(const std::string& s1, const std::string& s2) const {
        return s1+s2;
    }
};

std::string concatStrings(const std::string& s1, const std::string& s2) {
    return s1+s2;
}

allows creating and passing a delegate:

CppClass cpp;
og::ObjcClass objc("MyGlueClass");
objc.add_handler<NSString* (NSString*, NSString*)>
    ("concatString:withString:", &cpp, &CppClass::concatStrings);
// or using a free function:
objc.add_handler<NSString* (NSString*, NSString*)>
    ("concatString:withString:", &concatStrings);
[someInstance setDelegate:objc.get_instance()];

which can then be used:

NSString* result = [delegate concatString:@"abc" withString:@"def"];
assert([result compare:@"abcdef"] == NSOrderedSame);

Boost.Function objects can also be passed, which means Boost.Bind can easily be used as well.

While the basic idea works, this is still a prototype. I did a short blog post on the subject and the prototype source is available via bitbucket. Constructive input and ideas welcome.

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