How can i use Xcode project to call the function of Unity project

Questions & Answers
1

How can I use Xcode project to call the function of Unity project.
Because I write the Iphone project on Xcode,and I write the Iphone 3D project on Unity.
Is the Unity project put in the Xcode project?
How can I put two of projects together.

2

Lookup NativeToolkit by Prime31, I believe it has example of how to do this.

3

Thanks for your help.

4

Sorry, I have an error that is ‘mono_dl_register_symbol’ was not declared in this scope.
How can I solve this error?