ExternalObject questions

Robin_W_Mills@adobeforums.com wrote:
> There isn't a way to create static methods/properties with the CClientLib interface.

Ah, well. You can't have everything. But now that I've got a better idea what
the limitations are, I can work out ways around them.

Thanks for the info.

-X

Michael_Daumling@adobeforums.com wrote:
> 1) Currently, there is no way to add class elements. If you decide to add some ExtendScript to your DLL, you may want to add class methods that wrap calls into your DLL.
So I could implement class methods as a bit of code that (in turn) makes a call
to a method defined on the external object. I guess I can live with that.
Hopefully the inability to do something similar for normal class variables (as
opposed to constants defined as class variable) won't be too much of a problem.

>
> 2) I am afraid that I don't understand your question well enough.

Let's say that I have defined a class via the ExternalObject framework called
XFile. The dll defines one property called 'name' and three methods called
'open', 'read', and 'close'.
Ex:
var f = new XFile();
f.name = "somename";
f.open();
var str = f.read();
f.close();
alert(str);

Now, let's say that in using this class in a script, I want to add new
properties and methods like this:
var f = new XFile();

f.readFromFile = function(fname) {
if (this.cachedName == fname && this.cachedStr) {
return this.cachedStr;
}
this.name = fname;
this.open();
var str = this.read();
this.close();
this.cachedStr = str;
this.cachedName = fname;
return str;
}

var str = f.readFromFile("somename");
alert(str);

Or like this:
XFile.prototype.readFromFile = function(fname) {
// etc....
}

var f = new XFile();
var str = f.readFromFile("somename");
alert(str);


Will my Call function be invoked when "readFromFile" is called? Will my Put and
Get functions be called when I access "cachedName" and "cachedStr"? If so, what
do I do?


There is also this problem. Assume we have the XFile class as originally
defined. Now, let's insert a shim function:

XFile.prototype._oldRead = XFile.prototype.read;
XFile.prototype.read = function() {
if (this.cachedStr) {
return this.cachedStr;
}
this.cachedStr = this._oldRead();
return this.cachedStr;
}

This is not an unreasonable thing to do and is actually quite necessary in cases
where built-in methods are busted (as Folder.getFiles() was in PS7).
Given the current definition of the ExternalObject framework, I don't see how my
Call function could be invoked with any expectation that the correct thing is
going to happen. There ultimately must be a way of defining a function/method
that corresponds to a single specific callback on the C/C++ side; going through
a centralized Call function will only work in the most rudimentary
situations/class definitions.


-X
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