How can I pass a string value from C++ to JavaScript in a Windows environment using Visual Studio 2008?

In my current project, I have successfully implemented an IDL for passing a string value from JavaScript to C++. The JavaScript code effectively passes a string value to the C++/COM object.

[id(1), helpstring("method DoSomething")] HRESULT DoSomething([in] BSTR otlToken);

Now, I have a requirement to add another method that will return a string to a JavaScript caller. In order to achieve this, I made the following addition to the IDL:

[id(3), helpstring("method GetValue")]  HRESULT GetValue([out] BSTR *nicknames);

However, the developer working on the JavaScript side is encountering issues such as getting a message about the wrong number of arguments when trying to call the method or access it as a property.

My concern is whether JS requires a call by reference to retrieve this data, or if I should pass the one BSTR* param as [in,out].

What steps can be taken to make this functionality work? Specifically, how can we retrieve a string value from C++/IDL to a JavaScript caller?

I would appreciate guidance on what the IDL needs to look like and how the JavaScript code should be structured in order to achieve this desired outcome.

Answer №1

When dealing with Javascript, it is important to specify the return values from parameters. If you do not explicitly declare which parameter is the return value, COM will default to returning the HRESULT. One way to handle this is by using the code snippet below.

[id(2), helpstring("function FetchData")]  HRESULT FetchData([out, retval] BSTR *data);

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