Unity、iOS交互时，Unity调用iOS出错

Undefined symbols for architecture armv7:
"__PressButton1", referenced from:
RegisterMonoModules() in RegisterMonoModules.o
"__PressButton0", referenced from:
RegisterMonoModules() in RegisterMonoModules.o
ld: symbol(s) not found for architecture armv7
clang: error: linker command failed with exit code 1 (use -v to see invocation)

求助 要怎么解决啊？

我在unity里面注册了两个函数：
public class SDK

{

[DllImport("__Internal")]

private static extern void _PressButton0 (int RMB);

     public static void ActivateButton0 (int RMB)     
     {       
        _PressButton0 (RMB);     
     }     

     [DllImport("__Internal")]     
     private static extern void _PressButton1 ();     

     public static void ActivateButton1 ()     
     {     

        _PressButton1 ();     
     }     
} 

这是Xcode报的错？Xcode debug时，如果develop target版本与手机版本对不上会报这种architecture的错

补充一下，unity调用Xcode封装的函数，声明时需要用extern "C"；