Linking to a C++ native library in MonoTouch

问题:

I am reading up about linking native libraries into MonoTouch, specifically this documentation:

http://monotouch.net/Documentation/Linking_Native_Libraries

Here it describes linking to C libraries. Is it also possible to link to C++ libraries from MonoTouch? I am very new to MonoTouch and particularly to importing libraries, so I would appreciate any advice about problems I may face trying to import a C++ library, if this is indeed possible. Would wrapping the C++ library in an Objective-C library and then using btouch to import this be a good route to take? Or is there an easier approach? Bearing in mind that my knowledge of C++ (and Objective-C for that matter) can best be described as "dangerous". ;)

The reason that I ask is that I am needing to make use of a C++ API from Sybase to access their Ultralite database. I have managed to get a sample application that accesses the Ultralite C++ API working in Xcode, with Objective-C. But now I am trying to port this sample to MonoTouch. The sample application can be found here:

https://github.com/BruceHill/Ultralite-Names-Sample-ObjC

The Sybase documentation for Xcode mentions the following, with reference to using the API in Xcode:

This tutorial uses the UltraLite C++ API. In order to eliminate the need to cast to C types, compile the source as C++. To compile the project as C++:

1. In the Search in Build Settings box, enter Compile Sources As.
2. Choose Objective-C++ from the options in the Value field

What are the implications of this for working with this API in MonoTouch?

回答1:

You can certainly use a C++ api, but you will need to either wrap it in a C api, or a ObjC+btouch api to be able to talk to this. Invoking C api's uses PInvoke, and C++ libraries use symbol mangling. While theoretically you could pinvoke to the mangled symbol, this isn't a good idea as the mangling is compiler specific.