joe,
>> In this case _obj. foo (); can be used in other functions in
ext1Component too, in original case this._obj will be null if it is used
in other functions than init()
It is because 'createInstance' method makes new instance of
'ext1Component' object each time it is called.
There is yet another two ways to avoid 'null' value of '_obj' object field.
1) 'getService' method may be used istead of 'createInstance' method,
so only one instance of 'ext1Component' object will be created for all
windows; it is analogue of way you has proposed (global variable), and
here may be cross-windows 'callbacks': for example, window1 calls
'init', then window2 calls another component's method, but '_obj' points
to window1.
2) extension's object can have field to store 'ext1Component' instance,
for example:
var extobject =
{
mc: null,
init: function ()
{
this. mc = Components. classes...
this. mc. init (this);
},
go: function ()
{
this. mc. bar ();
}
};
In case 2) each window can have its own instance of 'ext1Component' object.
joe ertaba wrote:
Thank you very much Anton, examples helps me a lot.
In order for future reference for other developers I have one
modification in (/components/ext1component.js) for both ext1 & ext2
instead of:
function ext1Component ()
{
this. wrappedJSObject = this;
}
ext1Component. prototype =
{
QueryInterface: function (iid)
{
if (!iid. equals (Components. interfaces. ext1Component) &&
!iid. equals (Components. interfaces. nsISupports))
throw Components. results. NS_ERROR_NO_INTERFACE;
return this;
},
_obj: null,
init: function (obj)
{
this. _obj = obj;
// ...
this. _obj. foo ();
}
};
use this one:
*var _obj;*
function ext1Component ()
{
this. wrappedJSObject = this;
}
ext1Component. prototype =
{
QueryInterface: function (iid)
{
if (!iid. equals (Components. interfaces. ext1Component) &&
!iid. equals (Components. interfaces. nsISupports))
throw Components. results. NS_ERROR_NO_INTERFACE;
return this;
},
init: function (obj)
{
* _obj = obj;*
// ...
*_obj. foo ();*
}
};
In this case _obj. foo (); can be used in other functions in
ext1Component too, in original case this._obj will be null if it is
used in other functions than init()
-Joe
On Mon, Feb 2, 2009 at 12:02 AM, Anton Glazatov <[email protected]
<mailto:[email protected]>> wrote:
>> Is it possible to declare object variable into the idl file?
No, it isn't possible. Component method's argument should
implement any interface.
>> but I think I should reverse them, something like
Yes, you are right.
>> I don't exactly know why I need QueryIntrface here in my
extension js file beside in component
If you will use wrappedJSObject in your component constructor (see
here:
https://developer.mozilla.org/en/How_to_Build_an_XPCOM_Component_in_Javascript),
you need not to define extra interface for callback.
>> Would you please give me a sample extension file
You can see attached files. The ext1 doesn't use wrappedJSObject,
and ext2 use wrappedJSObject.
Btw, there is third way to call extension's function from xpcom
component - you may use global notifications (see
nsIObserverService / nsIObserver).
joe ertaba wrote:
Thanks Anton
Second method looks great, but I have few problems with it
or you may implement any interface in your extension's
object, it
may be somethink like
// xpcom .idl
...
interface YourComponent: nsISupports
{
...
void init (in YourComponentCallback obj);
...
};
interface YourComponentCallback: nsISupports
{
...
void foo ();
...
};
Is it possible to declare object variable into the idl file?
something like
interface YourComponent: nsISupports { void init (in object
obj); };
As I think it doesnt mean to declare object in idl! so I
should use your trick, but I think I should reverse them,
something like
// xpcom .idl
...
interface YourComponentCallback: nsISupports
{
...
void foo ();
...
};
interface YourComponent: nsISupports
{
...
void init (in YourComponentCallback obj);
...
};
// xpcom
...
extobject: null,
...
init: function (obj) { this. extobject = obj; },
...
bar: function () { this. extobject. foo (); }, // call
extension's
function
...
// extension
var yourextensionobject =
{
...
init: function () {
var mycomponent = Components. classes ["@yourcomponent.cid"].
createInstance (Components. interfaces. YourComponent);
mycomponent. init (this);
},
...
foo: function () { ... },
...
QueryIntrface: function (iid)
{
if ((!iid. equals (Components. interfaces. nsISupprots) &&
(!iid. equals (Components. interfaces.
nsIYourComponentCallback))
Components. results. NS_ERROR_NO_INTERFACE;
return this;
}
I don't exactly know why I need QueryIntrface here in my
extension js file beside in component, if it helps to declare
object (YourComponentCallback) then is it enough or some other
things also needed (in xpcom we need lots of other thing like
Factories, Modules,... )
Maybe I am somehow confized! because I never see idl &
QueryIntrface for normal js (not compont)
Would you please give me a sample extension file or at least
some toturial which explain these concepts :)
Thanks in advance
Joe
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