Unity call c# code from c/objective-c part

• Method 1: use UnitySendMessage("[gameobject_name]", "[method_name]", "[string_param]");
  The above code equal the following code:

GameObject.Find("[gameobject_name]").SendMessage("[method_name]", "[string_param]");

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To receive message, this gameObject must have a Monobehavior script that must implement a method like this:

public void method_name(string str) {
    //  some logici here
}

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If several scripts implement such method, all of them will be called.

• Method 2: use delegate to register a callback function in C# side, this need to write some code both for c# and c/objective-c sides.
  Here is the work for C# side:

private delegate void OnViewClosed(int result, string msg);

[MonoPInvokeCallback(OnViewClosed)]
static void CalledByNativeC(int result, string msg)
{
    // some logic here
}

// ... 

#if UNITY_IOS
[DllImport("__Internal")]
private static extern void SetOnViewClosed(OnViewClosed);
#endif

// register the callback function
SetOnViewClosed(CalledByNativeC); 

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The following is the code for c/objective-c side:

#include <stdlib.h>
#ifdef __cplusplus 
extern "C" { 
#endif

// define as a function pointer type
typedef void (*OnViewClosed)(int result, const char* msg);

// keep the function pointer
static OnViewClosed s_calledFromCSharp = NULL;

// called from c# code
void SetOnViewClosed(OnViewClosed viewClosed)    
{
    s_calledFromCSharp = viewClosed;
}
 
// ......
// some where in C/Objecive-C, trigger the callback function
   if (s_calledFromCSharp != NULL)
       s_calledFromCSharp(result, msg);
//......

#ifdef __cplusplus 
} 
#endif  

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