- first, the second argument to widget.system is a reference to a
function, not an actual function call. Leave off the brackets, (), to
pass the function as an argument. Currently you are passing it the
result of the function which is being called immediately.
Didn't realize that I referenced a call when I should have referenced an object.
- second, when using an asyncronous call the results of the
call are passed as an argument to the function called, so
_temporarySystemCall is not needed.
Thanks for clearing that up, I didn't know/understand that either.
- third, since this is a
method of an object you will want to pass it a bound reference to the
method since _javascript_ has a nasty habit of changing the definition of
'this'. I prefer to use bind() from prototype.js since it is simple and
licensed such that it can be recopied at will.
I have noticed that 'this' sometimes is more like 'that'... I have created a workaround for XMLHttpRequest but I did not really realize what I worked around I guess. It might have been because of a redefinition of 'this'.
If you'd like to take my advice then your call will become this:
widget.system
("/usr/bin/id -un", this._temporaryGetUserName.bind(this));
Hope that helps,
N
It did help and the widget is working now :-)
I acctually tried both with and without brackets on the call to
widget.system before but both crashed. I think I understand why now.
The reason it did crash without brackets was probably because _javascript_ redefined 'this'. Using bind() fixed this.
Also I got an undefined value when I used brackets because (as Glenn Andreas pointed out in a mail that I think only came to me) when using brackets, the command would be run once before the
widget.system call. And if it runs before widget.system it will of course don't have anything to work with.
Thanks for all your help!
Gustav
I'm trying to call widget.system asynchronously from a _javascript_ object but I cannot get it to work properly.
It does work if I specify null instead of an endhandler but since we are not supposed to use null anymore I would like to do it "the proper way" even from within an object.
Here is the problematic section of my source code (_temporaryGetUserName crashes the widget):
function XmltvBack() {
this._userID = "";
this._temporarySystemCall;
this._doneButton = new AppleGlassButton(
document.getElementById("backDoneButton"),"Done",this.doneButtonPressed());
this._usersChannels = new Array();
this._usersChannelsHash = new Array();
this._channelsXmlIsReady = false;
this._channelsXml;
this._temporaryInstaller();
}
var globalXmltvPath;
XmltvBack.prototype._temporaryInstaller = function(){
document.getElementById("debug").innerHTML = "_temporaryInstaller körs";
if(window.widget){
document.getElementById("debug").innerHTML = "username = "+widget.system("/usr/bin/id -un", null).outputString; // Works!
this._temporarySystemCall =
widget.system("/usr/bin/id -un", this._temporaryGetUserName()); // Does start the endHandler but this._temporarySystemCall is undefined - why? :-(
} else
this._temporaryGetUserName();
}
XmltvBack.prototype._temporaryGetUserName = function(){
document.getElementById("debug").innerHTML = "_temporaryGetUserName running";
if(window.widget){
document.getElementById
("debug").innerHTML = "_temporaryGetUserName is about to save this._userID";
this._userID = ""+this._temporarySystemCall.outputString; // Row 29. Crashes the widget since this._temporarySystemCall is undefined
document.getElementById("debug").innerHTML = "userID= "+this._userID;
} else {
this._userID = "gusax840";
alert("_continueStartup running");
}
globalXmltvPath = "/Users/"+this._userID+"/Library/Xmltv/";
this._channelsXml = new XmltvChannelsXml(globalXmltvPath+"server/channels.xml",this);
}
I've attached the widget as a zip file. The above code can be found in _javascript_/XmltvBack.js starting on row 1. Please note that the widget will crash on row 29 if you open it in Dashboard. It works in Safari though, if you want to see how it should look like.
Gustav
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