Read Individual Data from array collection

Question

I used var dp:ArrayCollection = new ArrayCollection(container.GetVotesResult); to get the JSON data from GetVotesResult method. I get the values as below.

{"GetVotesResult":
[{"Aid":0,"Arank":0,"Atext":null,"ClientId":16,"Votes":0,"qid":10,"qtext":"Who will win 2011 football world cup?"},
{"Aid":4,"Arank":1,"Atext":"yes","ClientId":null,"Votes":0,"qid":null,"qtext":null},
{"Aid":5,"Arank":2,"Atext":"no","ClientId":null,"Votes":0,"qid":null,"qtext":null},
{"Aid":6,"Arank":3,"Atext":"i don't know","ClientId":null,"Votes":0,"qid":null,"qtext":null}]}

I am able to retrieve the 1st array data after looping the dp arraycollection list.

if(i==0)
{
 trace("Show me:",obj.qtext);
}
O/P: Show me: Who will win 2011 football world cup?

How do I retrieve the 2nd, 3rd, 4th and so on (if it has) array datas individually and dynamically. Say, I want to take 'Atext' from all the array. Please help. I use flashbuilder4.5..

Answer 1

From your output above, GetVotesResult is an Array of Objects which you can iterate over using a for / for each loop, eg:

var result : String = "";  // JSON String omitted for brevity

// Decode the JSON String into an AS3 Object graph.
var data : Object = JSON.decode(result);

// reference the GetVotesResult Array from the result Object.
var votes : Array = data["GetVotesResult"];

// Iterate over each 'Vote' object in turn and pull out the 
// 'Atext' values the objects contain into a new Array.
var Atexts : Array = [];
for each (var vote : Object in votes) 
{
    // Check for the existance of the 'aText' property.
    if (vote.hasOwnProperty("Atext")) {
        Atexts.push(vote.Atext);
    }
}

// Dump out all the aText values: (,yes, no, i)
trace("Atexts: " + Atexts.join(", "));

Alternatively you may wish to copy the objects into a Map Data Structure (a Dictionary in AS3) to create a lookup table based on one of the Keys:

// Create a new, empty Lookup Table.
var votesByAid : Dictionary = new Dictionary();

// Iterate through the Vote Objects and add each one to the 
// lookup table based on it's Aid property.
for each (var vote : Object in votes) 
{
    // Check for the existance of the 'aId' property to stop
    // any 'nulls' getting into our Lookup Table.
    if (!vote.hasOwnProperty("Aid")) {
        trace("Vote Object did not contain an `Aid` property.");
        continue;
    }

    // Add the entry to the lookup table.
    var key : String = vote.Aid;
    votesByAid[key] = vote;
}

// You can now use the lookup table to fetch the Vote Objects.
trace(votesByAid[6].Atext); // traces 'i don't know'

Answer 2

this can get all String from that object

for(var i=0;i<data.length;i++){
        for(var key in d){
        if(d[key] instanceof String)
            trace(d[key]);
    }
}

Answer 3

You can use filter() and map() to create new arrays of the data you need.

Let's assume you're already getting the JSON data into in arrayCollection (or array), so for this example I'm just creating the array:

private var GetVotesResult:Array = [{"Aid":0,"Arank":0,"Atext":null,"ClientId":16,"Votes":0,"qid":10,"qtext":"Who will win 2011 football world cup?"},
{"Aid":4,"Arank":1,"Atext":"yes","ClientId":null,"Votes":0,"qid":null,"qtext":"Who stole my socks?"},
{"Aid":5,"Arank":2,"Atext":"no","ClientId":null,"Votes":0,"qid":null,"qtext":null},
{"Aid":6,"Arank":3,"Atext":"i don't know","ClientId":null,"Votes":0,"qid":null,"qtext":null}];

Now you can use Array.filter to create a new array that only contains elements that have a valid value for the desired field:

//Get an array with elements that have the desired property:
public function getElementsWithProperty( propName:String ):Array {
    return GetVotesResult.filter( elementHasProp( propName ) );
}
private function elementHasProp( propName:String ):Function {
    return function( element:Object, index:int, array:Array ):Boolean {
        return ( element[ propName ] != null );
    }
}

To test the above:

var elementsWithQText:Array = getElementsWithProperty( 'qtext' );

trace( 'Values of qtext in elementsWithQText array: ' );
for each ( var element:Object in elementsWithQText ) {
    trace( element.qtext );
}
//OUTPUT:
//Values of qtext in elementsWithQText array: 
//Who will win 2011 football world cup?
//Who stole my socks?

Or, you can use Array.map to create an array of only values for a certain property:

//Get an array of only a certain property:
public function makeArrayOfProperty( propName:String ):Array {
    return GetVotesResult.map( valueOfProp( propName ) );
}
private function valueOfProp( propName:String ):Function {
    return function( element:Object, index:int, array:Array):String {
        return element[ propName ];
    }
}

You can test the map function above with:

var valuesOfAtext:Array = makeArrayOfProperty( 'Atext' );
trace( 'Values of valuesOfAtext: ' + valuesOfAtext );
//OUTPUT: Values of valuesOfAtext: ,yes,no,i don't know

This page does a great job describing map, filter, and the rest of Array: http://www.onebyonedesign.com/tutorials/array_methods/