That would make sense, but I'm actually seeing something else. Thanks
in advance for any help with this!
I put in trace statements in all the methods of my dataProvider and
the output below is what I get when a simple app with a DataGrid
starts up. The Constructor is called, the getItemAt() with an index
of 'undefined', then get length() is called a bunch of times and
returns 5 each time, then getItemAt(0), etc, etc.
(The code for the getItemAt method follows the trace.)
[Debug] DPTest initialized
[Debug] TestDP(undefined)
[Debug] getItemAt(undefined)
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] getItemAt(0)
[Debug] getItemAt(1)
[Debug] getItemAt(2)
[Debug] getItemAt(3)
[Debug] getItemAt(4)
[Debug] getItemAt(5)
[Debug] getItemAt(6)
[Debug] getItemAt(7)
[Debug] getItemAt(8)
[Debug] getItemAt(9)
[Debug] getItemAt(10)
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
[Debug] get length():5
Here's the actual code of my dataProvider.getItemAt method. The
DataGrid displays the Names from "0 - .." to "4 - ..", skipping
the "Undefined 1234" name.
(Note: the reason for writing this method like this is to try and
understand the interaction between the dataProvider and its users.)
function getItemAt(index : Number)
{
Echo.debug('getItemAt(' + index + ')');
if(index==undefined){
var o:Object = new Object();
o.Name = "Undefined 1234";
return o;
} else if(index==0){
var o:Object = new Object();
o.Name = "0 - 1234";
return o;
} else if(index==1){
var o:Object = new Object();
o.Name = "1 - 1234";
return o;
} else if(index==2){
var o:Object = new Object();
o.Name = "2 - 1234";
return o;
} else if(index==3){
var o:Object = new Object();
o.Name = "3 - 1234";
return o;
} else if(index==4){
var o:Object = new Object();
o.Name = "4 - 1234";
return o;
} else {
return null;
}
}
--- In [email protected], "Matt Chotin" <[EMAIL PROTECTED]> wrote:
> I'd imagine that if you're seeing numerous calls to length
interspersed
> with getItemAt that we simply didn't do an optimal loop.
>
>
>
> for (var idx = 0; idx < dataProvider.length; ++idx)
>
> {
>
> var item = getItemAt(idx);
>
> }
>
>
>
> get length() is going to be called on every iteration of the loop.
It'd
> obviously be more efficient to store length in a local variable and
just
> use that, but maybe we didn't somewhere.
>
>
>
> Matt
>
> ________________________________
>
> From: [email protected]
[mailto:[EMAIL PROTECTED] On
> Behalf Of rbelknap
> Sent: Friday, June 03, 2005 3:24 PM
> To: [email protected]
> Subject: [flexcoders] Contract between DataProvider and ComboBox or
> DataGrid
>
>
>
> Hi,
>
> I'm struggling to figure out the implied contract between
> DataProviders and their users like ComboBox or DataGrid. When
either
> a ComboBox or DataGrid first uses a DataProvider they seem to make
> numerous calls to:
>
> public function get length():Number
>
> and
>
> function getItemAt(index : Number)
>
> but it isn't obvious what the logic is behind these calls.
>
> I was expecting to see a call to get the length followed by a
series
> of calls to getItemAt starting at index 0 and running to index
length-
> 1, but that's not what I see.
>
> Has anyone run across any good discussions of DataProviders and
their
> users?
>
> Thanks,
>
> Randy
>
>
>
>
>
>
> ________________________________
>
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