How to transfer complex data structure from iOs native extension to HaXe?

Haxe
#1

Hello!

I have, let’s say, NSArray containing NSStrings in my objective c code of native extension. I need to have it in HaXe code as Array<String>. What is the right way to transfer it?

As far as i understand, i need first to transfer it to some function in cpp code (declared in ExternalInterface.cpp) which then calls (via val_call) HaXe callback and passes data to it. I’m pretty sure there is no way to transfer NSArray or even just NSString as is. But i cannot figure out how to convert it to something that can be passed through.

I’ve found from other extensions source code that NSString should be passed as const char* via [myNSStringVar UTF8String], but still have no idea on how to pass array.

Thanks in advance!

#2

This is the sort of thing JSON is designed for.

  1. Convert your NSArray to JSON.
  2. Pass it to Haxe.
  3. Parse it.
  4. Done!
1 Like
#3

Here’s a little example of allocating a Haxe array on the C++ side:

You should be able to use alloc_string or alloc_wstring if you convert the NSString to const char*, std::string or a wstring

1 Like
#4

Great advice, thanks!

This definitely should do the trick on transferring small structures. But in cases of some “big data” JSON could fail. I’ve tried to pack ~140kb string to JSON recently on neko target - failed as expected.

Anyway, packing to JSON reflects “keep it simple stupid” approach. And sometimes it is all we really need. :wink:

#5

It is exactly what i was seeking!

And i’ve just took a look at hx/CFFI.cpp in hxcpp project - good place to learn how allocs and vals are working. It isn’t documented well at the moment, am i right? At least i cannot find available documentation for this.

I’ll describe and share my solution on topic after implementation.

Thanks, @singmajesty!

#6

Yeah, I look at sources :wink:

Also http://nekovm.org/doc/ffi :slight_smile:

#7

Aw! Thank you for the right link, things are much clearer now. Very useful indeed.

I didn’t found this before as i was googling for “haxe alloc_array” and there’s only one mention of “haxe” on the page: “Haxe Foundation” in footer. :smiley: