[TIMOB-24435] Windows Module: Receive C++ callback from JS

GitHub Issue	n/a
Type	Improvement
Priority	None
Status	Closed
Resolution	Invalid
Resolution Date	2017-03-22T01:18:11.000+0000
Affected Version/s	Release 6.0.1
Fix Version/s	n/a
Components	Windows
Labels	n/a
Reporter	Ricardo Ramirez
Assignee	Kota Iguchi
Created	2017-02-27T22:55:22.000+0000
Updated	2017-03-22T01:18:11.000+0000

Description

Issue Description

Customer need a way to receive a function (callback) from Javascript in the C++ code by looking at the code in TitaniumKit. Formerly, in Kroll, this would be done by doing something like: (Assuming this is an android module) HashMap args = args; KrollFunction someFunction = (KrollFunction) args.get("someFunction"); [...] someFunction.call(KrollObject, KrollDict); So Would it be possible you provide an example on this if is possible?

Comments

Kota Iguchi 2017-02-28

Yes it's possible, you can find examples in TitaniumKit because callback pattern has been used a lot in Titanium API. I think easiest way to fire callback is leveraging addEventListener. For instance [Ti.Gesture](https://github.com/appcelerator/titanium_mobile_windows/blob/master/Source/Sensors/src/Gesture.cpp#L28). So let say you are listening somethingfired event. In this case you can add listener in JavaScript

   var YOUR_MODULE = require('YOUR_MODULE'), 
         your_module = new YOUR_MODULE();
   your_module.addEventListener('somethingfired', function(e) {
      Ti.API.info(e.type + ' my_number:' + e.my_number);
   });

You can fire this callback from the module by executing fireEvent like below.

   TITANIUM_FUNCTION(YourModule, doTheMyNumberEvent)
   {
       const auto ctx = get_context();
       auto e = ctx.CreateObject();
       e.SetProperty("my_number", ctx.CreateNumber(12345));
       fireEvent("somethingfired", e);
   }

There is another way to do the callback, by calling JSObject as a function directly. This is basic functionality within [HAL](https://github.com/appcelerator/HAL) framework.

   var YOUR_MODULE = require('YOUR_MODULE'), 
         your_module = new YOUR_MODULE();
   your_module.doTheCallbackImmediately(function(str) {
      Ti.API.info(str);
   });

   TITANIUM_FUNCTION(YourModule, doTheCallbackImmediately)
   {
   	ENSURE_OBJECT_AT_INDEX(my_callback, 0);
   
          const std::vector<JSValue> args { get_context().CreateString("TEST") };
   	my_callback(args, get_object());
   	return get_context().CreateUndefined();
   }

Example: https://github.com/appcelerator/HAL/blob/master/examples/Widget.cpp#L277

Ricardo Ramirez 2017-02-28

Thank you Kota !
Kota Iguchi 2017-03-22

Closing this for now, this is implemented by HAL framework.

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