CODEWITHSUNDEEP
c++firefoxfirefox-addonxpcom
frinux
frinux

Reputation: 2092

XPCOM object method is unaccessible from JavaScript

I'm trying to build an extension for Firefox. This extension uses an XPCOM component (a C++ dll). I'm compiling the DLL, compilation is OK.

I also succeeded in building a JS code which instanciates the object from XPCOM:

try {
   greenfox;
   return true;
} catch( e ) {
   alert( e );
   return false;
}

The object returned is this one:

QueryInterface
    QueryInterface()

__proto__
    [xpconnect wrapped native prototype] { QueryInterface=QueryInterface()}

QueryInterface
    QueryInterface()

Everything is fine, except I can't call the function which are supposed to be in my XPCOM component.

Here is my IDL file:

[scriptable, uuid(ec8030f7-c20a-464f-9b0e-13a3a9e97384)]
interface nsISample : nsISupports
{
    attribute string value;
    void writeValue(in string aPrefix);
    void poke(in string aValue);

    void start();
    double stop();
};

When callingstart() function, I get the Javascript error: "is not a function"

greenfox.start();

Do you have any idea? It seems like no function is exposed in my XPCOM.

Upvotes: 1

Views: 769

Answers (2)

Wladimir Palant
Wladimir Palant

Reputation: 57651

You seem to be looking at an object exposing only the nsISupports interface. Your interface (nsISample) won't get exposed by default, you have to explicitly request it. You can do it for example by instantiating your component like this:

var greenfox = Components.classes["..."].getService(Components.interfaces.nsISample);
greenfox.start();

Alternatively, you can also call QueryInterface on an object you already have:

greenfox.QueryInterface(Components.interfaces.nsISample);
greenfox.start();

Generally, I wouldn't recommend using a binary XPCOM component for reasons outlined here, maintaining them requires way too much effort. I would rather suggest compiling a regular DLL and using it via js-ctypes. Reference a binary-component to js-ctypes mentions how you would locate a DLL inside your add-on to use it via js-ctypes.

Upvotes: 1

artificialidiot
artificialidiot

Reputation: 5369

Do you call QueryInterface with your uuid? It is necessary to call it before using the component instance created. Does your usage match what's in here?

If you don't want to deal with XPCOM you can use js-ctypes.

Upvotes: 0

Related Questions