Flex 3: Can anybody see why this dictionary isn't working? - apache-flex

Question

So, in my main mxml, i have a variable defined as such:
[Bindable] public var studentsListDict:Dictionary = new Dictionary;
I also have the following imported:
import flash.utils.Dictionary;
I then have an HTTPService that imports an XML file:
<mx:HTTPService id="studentsHttp" url="students.xml" resultFormat="e4x" makeObjectsBindable="true" result="createStudentsCollection(event)" />
The createStudentsCollection function is as follows:
private function createStudentsCollection(e:ResultEvent):void
{
var xmlList:XMLList = XML(e.result).student;
var dupString:String = "|";
var tempArray:Array = new Array;
studentsListDict = new Dictionary;
for (var i:int = 0; i < xmlList.length(); i++)
{
if (dupString.indexOf(String("|" + xmlList[i].name) + "|") == -1)
{
tempArray = new Array;
tempArray[0] = xmlList[i].name.#id;
tempArray[1] = xmlList[i].name;
tempArray[2] = xmlList[i].year;
tempArray[3] = xmlList[i].track;
studentsListAC.addItem(tempArray);
studentsListDict[tempArray[0]] = tempArray;
dupString += "|" + xmlList[i].name + "|";
getLen(studentsListDict);
}
}
}
Then, to ensure the items were correctly put into the dictionary, i have the following function:
public static function getLen(d:Dictionary):int
{
var i:int = 0;
for (var key:Object in d)
{
Alert.show(String(key + "\n" + d[key]));
i++;
}
return i;
}
This creates pop up alerts that show that everything was loaded correctly into the dictionary.
Later on, in a child, I call a function that tries to use the dictionary, and i get a return of "undefined".
Here's the function that searches based on key, and returns a value from the array within:
public function getStudentName(sID:Number):String
{
return studentsListDict[sID][1];
}
Unfortunately, the getStudentName function simply returns undefined every time.
If anybody can see something I'm missing, it'd be greatly appreciated.
Thanks,
Brds
EDIT
It wasn't working b/c you can't have numbers as keys in a dictionary. Simply casting them to a string during the declaration and look up seems to work just fine.

Answer 1

Here is some documentation on dictionary keys..
It looks like you're code is setting it as a string and then accessing it as a number. I suspect that is the root of your problem You can try something like this:
public function getStudentName(sID:Number):String
{
return studentsListDict[sID.toString()][1];
}
It is actually perfectly acceptable to use numbers as Keys to a Dictionary. The Dictionary apparently turns the number and a string value of that number to the same key. Here is a sample:
<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600" creationComplete="application1_creationCompleteHandler(event)">
<fx:Script>
<![CDATA[
import mx.events.FlexEvent;
public var dict : Dictionary;
protected function application1_creationCompleteHandler(event:FlexEvent):void
{
dict = new Dictionary();
dict["0"] = "hi";
dict["4"] = "hola";
dict["17"] = "bye";
dict["32"] = "adios";
dict[32] = "adios 2";
dict[3.2] = "adios 3";
dict[50] = "Audio ";
dict["50"] = "Audio 2";
trace(dict["0"]);
trace(dict["4"]);
trace(dict["17"]);
trace(dict["32"]);
trace(dict[32]);
trace(dict[3.2]);
trace(dict[50]);
trace(dict["50"]);
}
]]>
</fx:Script>
</s:Application>

Answer 2

I think it's because getStudentName is using a Number as a key, while createStudentCollection is using a string. In this case, because the keys are numbers/strings, you can simply use an Object: var studentsListDict:Object = {}; — it will automatically coerce all the keys to strings.
Also, as an asside: new Dictionary(); more standard, and it's better form in ActionScript to use [] (eg, var foo:Array = []) than new Array(). That way you can put stuff in the array at the same time:
var tempArray:Array = [
xmlList[i].name.#id,
xmlList[i].name,
…
];