Unity receive event from object c

Question

I want to create a ios plugin for unity. The function is send textmessage using some sdk. Well, here is my object c:

-(TextMessage*) CsendText:(NSString *)number CmsgContent:(NSString *)msg{
    return [MessagingApi sendText:(NSString*) number msgContent:(NSString *) msg]
}

and here is my c wrap code :

TextMessage* SendMessage(const char* contactNumber,const char* content){
    Messaging* msg = [[Messaging alloc] init];
    NSString* nr = [NSString stringWithUTF8String:contactNumber];
    NSString* contentText = [NSString stringWithUTF8String:content];
    TextMessage* newText = [msg CsendText:nr CmsgContent:contentText];

    return newText;
}

you can see i return a textmessage, it is an event not a char,, how can i pass the event to unity,

my c# code is here:

#if UNITY_IPHONE
        [DllImport("__Internal")]
        private static extern string SendMessage (string contactNumber,string content);

#endif
    string phoneNumber="";
    string content="";
    void OnGUI () {
                phoneNumber = GUI.TextField ( new Rect (250, 125, 250, 25), phoneNumber, 40);
                content = GUI.TextField (new Rect (250, 157, 250, 25), content, 40);

        if (GUI.Button(new Rect (250, 250, 100, 30),"click me")) {
            SendMessage(phoneNumber,content);
        }

    }       

Answer 1

That's not the way it is working. You cannot just return something in C and expect it to appear in Unity / C#. To achieve a "two way communication" you'll need to do the following.

---

Unity => iOS

C# code

[DllImport ("__Internal")]
private static extern void _SomeCMethod(string parameter);

(Objective-) C code

void _SomeCMethod(const char *parameter) 
{
}

When you invoke _SomeMethod in C#, _SomeMethod in your (Objective-) C code gets called.

iOS => Unity

Objective-C code

- (void)callSomeCSharpMethod
    UnitySendMessage("GO", "SomeCSharpMethod", "parameter");
}

C# code (MonoBehaviour script attached to GO)

void SomeCSharpMethod(string parameter)
{
}

When you invoke callSomeCSharpMethod in Objective-C, SomeCSharpMethod in your C# code gets called.

---

Converting strings

You'll have to convert your NSStrings to c strings (const char *) and vice versa.

const char * => NSString

[NSString stringWithCString:string encoding:NSUTF8StringEncoding];

NSString => const char *

[string cStringUsingEncoding:NSUTF8StringEncoding];

---

Note: This is just a simple example on how to achieve a two way communication channel between C# and native iOS code. Of course you don't want to hardcode e.g. the GameObject's name in your code, so you can just pass that name (for callbacks from Objective-C) to your native iOS code at the very beginning.