On May 14, 11:32 am, nimrod <[email protected]> wrote:
> Hi Andrew,
>
> Thank you for your reply!
>
> I'm a bit puzzled...GDownloadUrl is asynchronous, yes...
> Still a newbie and I need to ask...my callback-function in this
> case...what is that?
The callback function, which is the function to which GDownloadUrl
passes its data once it's retrieved it, is referenced inside the
GDownloadUrl() call:
GDownloadUrl(url, function)
You can write a function called say, processMyData and have it as a
standalone function in your script:
function processMyData(passedData) {
...
}
[note that it accepts some data]. If you do that, you call it like
this:
GDownloadUrl(url,processMyData)
Note there are no brackets after processMyData in that form. You just
provide the name of the function. GDownloadUrl calls that function
when it's got the data and passes the data as the argument to the
function. processMyData receives the data as "passedData".
OR
You can write the function inside the GDownloadUrl call itself:
GDownloadUrl(url, function(passedData) { ... })
This is called an anonymous function because it doesn't have a name.
You just define the function with its argument.
You've used this second version, and the function receives the data
into a variable called "data". You parse "data" and assign the result
to a variable called "xml". That's all that happens.
After the GDownloadUrl() is started in the background, the code goes
on to try and do things with "xml". All of that stuff needs to go
inside the callback function.
You may find it easier to write a separate function which handles the
data, as the first way outlined above. You can almost certainly just
extract all the code which deals with the data out of where it is at
the moment and into a separate function. Call it processMyData(data):
function processMyData(data) {
var xml = GXml.parse(data);
var markers = xml.documentElement.getElementsByTagName("marker");
// etc
}
and then do the GDownloadUrl like
GDownloadUrl( ...,processMyData)
You'll need to put your url where I've got dots here.
Andrew
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