Consume WinJS.Promise (or equivalent) in C++ code

Question

I'm writing and a hybrid application in JavaScript/HTML5 for UI and C++ for backend processing. At one point I need to generate a user prompt from the C++ code and have it wait for user response.

When initializing my C++ object I pass a JavaScript callback function that takes prompt parameters and returns a WinJS.Promise that is fulfilled when the user responds. However call to that function fails in C++ with exception 0x800A000D (type mistmatch).

I assume that it is related to me trying to return a promise.

I've tried these function signatures and both don't work

IAsyncOperation<int>^ promptCallbackType(Platform::String^ text);

Platform::Object^ promptCallbackType(Platform::String^ text);

What is the proper way for passing a WinJS.Promise or something functionally equivalent to C++ code?

Answer 1

Hi,

I think this document can help you.
http://msdn.microsoft.com/en-us/library/windows/apps/xaml/hh755833.aspx
You can follow the codes in that document to call a C++ async function in JS.

Also, this document will help you to pass other data type from C++ to JS.
http://msdn.microsoft.com/en-us/library/windows/apps/xaml/hh441569.aspx

Best regards,
Jesse

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Jesse Jiang [MSFT]
MSDN Community Support | Feedback to us

Answer 2

Jesse,

Thank you for the links. I'm actually looking to do the opposite - I need to call a JS async function from C++

Answer 3

Hi,

As far as I know, the JavaScript cannot write component, so that we cannot use JS function directly.

But if we want to call JS function, we can use create a event in C++ and then add listen a function for this event. Fire this event in C++, so that the listener will be called in JS.
 
Best regards,
Jesse

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Jesse Jiang [MSFT]
MSDN Community Support | Feedback to us