Plugins - Sending String Data

Unity Engine
1

I tried this thread in the iOS section but no-one had a clue.

Is it possible to send string data to a C plugin from Unity? If so what type should the C script be expecting?

Im currently using the following:

[DllImport ("__Internal")] 
public static extern void ActivateTutorial( string description );

and the C Script:

extern 'C'
{
    void ActivateTutorial(  what magical type goes here? Im assuming char *  );
}
2

The code there is correct this way yeah.
sending over is char * and then using the NSString functions to get a string from utf8

the way back goes over cocoaToMonoString

3

Thanks. Solved in seconds.

4

This is probably more appropriate for the iOS forum, but Iā€™m hoping someone following this thread knows the answer. Whatā€™s the non-pro equivalent of cocoaToMonoString? I canā€™t seem to find that function in my project.

Iā€™m just string to get out the marketing version string like so:

	const char* getMarketingVersionString()
	{
		NSString *versionStr = [[NSBundle mainBundle] objectForInfoDictionaryKey:@"CFBundleShortVersionString"];
		return [versionStr UTF8String];
	}

But calling the function triggers this error: malloc: *** error for object 0x5c9ca90: pointer being freed was not allocated

5

The function is the same. iOS plugin support is license independent, its the same for both.

But you need to declare the extern function etc.

6

Yes, Iā€™ve wrapped my objective-C side function in an extern ā€œCā€, but Xcode complains: ā€œā€˜cocoaToMonoStringā€™ was not declared in this scope.ā€ Where is this function defined? I canā€™t seem to find it when I try to find-in-files.

7

I found my answer in the Bonjour plugin sample. I thought I needed to alloc/init a new NSString before returning the C-string, but a simple malloc will do:

// Helper method to create C string copy
char* MakeStringCopy (const char* string)
{
	if (string == NULL)
		return NULL;
	
	char* res = (char*)malloc(strlen(string) + 1);
	strcpy(res, string);
	return res;
}
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