How to find an ArrayCollection item with a specific property value?

I have some XML structures like this:

var struct:XML = <mh>
  <mi id="1" stuff="whatever"/>
  <mi id="2" stuff="whatever"/>
  <mi id="3" stuff="whatever"/>
</mh>;

I know I can access a subnode by "id", in this way:

var stuff:Object = struct.(hasOwnProperty('@id') && @id == '2').@stuff;

Now I have some similar ArrayCollection structure:

private var cmenu:ArrayCollection = new ArrayCollection([
    {id:"1", stuff:"whatever"},
    {id:"2", stuff:"whatever"},开发者_高级运维
    {id:"3", stuff:"whatever"}
]);

I wonder if items can be accessed in a similar way, like this:

var stuff:Object = cmenu['id == 2'].stuff;

Is it possible?

---

You can generalize Matt's answer a bit so that you can pass in the ID value you want instead of hard-coding it, and only need a single line to get your match (I assume you may want to do this in multiple places).

First you'd write a function to generate your find function:

function findId(id:int):Function {
  return function( element : *, index : int, array : Array ) : Boolean
  {
    return element.id == id;
  }
}

Then I'd write a function to return the first match so you don't have to duplicate the two lines:

function findInCollection(c:ArrayCollection, find:Function):Object {
  var matches : Array = c.source.filter( find );
  return ( matches.length > 0 ? matches[0] : null );
}

Then you'd just do this:

var stuff:String = findInCollection(cmenu, findId(2)) as String;

---

I've always used filterFunctions for ArrayCollections:

private var cmenu:ArrayCollection = new ArrayCollection([
    {id:"1", stuff:"whatever"},
    {id:"2", stuff:"whatever"},
    {id:"3", stuff:"whatever"}
]);

function getItemFromCollection(id:String):Object {
    var cmenuFiltered:ArrayCollection = new ArrayCollection(cmenu.toArray());

    cmenuFiltered.filterFunction =
        function(item:Object):Boolean {
            return item.id == id;
        }

    cmenuFiltered.refresh();

    return cmenuFiltered.getItemAt(0);
}

---

No, you can't. struct.mi.(@id == "2").@stuff is E4X which is short for ECMA Script for XML. You can't use e4x on other AS objects.

---

If you look at the docs for the Array class, you'll find several routines that aid in this, but none as concise as the e4x syntax used by the built-in XML data type. The filter() method in particular sounds like it might be the best fit for your example.

Here's a sample for how you might do this, given your setup.

var matches : Array = cmenu.source.filter( findId2 );
var stuff : Object = ( matches.length > 0 ? matches[0] : null );

...and the callback function findId2:

function findId2( element : *, index : int, array : Array ) : Boolean
{
    return element.id == 2;
}

---

You can actually go a little bit further and roll the filter function up into the findInCollection function. This means you can just pass the ArrayCollection, property name, and value in the same call:

public function findInCollection(c:ArrayCollection, 
                       propertyName:String, propertyValue:*):Array {

    var matches : Array = c.source.filter( 
               function( element : *, index : int, array : Array ) : Boolean {
                 return element[propertyName] == propertyValue;
               } 
            );

    return matches; 

}

var ac:ArrayCollection=new ArrayCollection(
                [{name:'Ben', id:1, age:12},
                    {name:'Jack', id:2, age:22},
                    {name:'Jill', id:4, age:22},
                    {name:'Joe', id:3, age:17}
                ]
            );
var searchedElements:Array=findInCollection(ac,'age',22);

Returns an array containing the 'Jack' and 'Jill' objects.

Obviously this only works if you are looking for a single property value, but if you wanted to search on multiple properties it would be possible to pass through an object containing the properties and values to search for.

---

You can even more generalize Herms answer by adding the property name in the function like this and thus getting a rather generic way of searching by property in an ArrayCollection

private function findInCollection(c:ArrayCollection, findFunction:Function):Array
{
 var matches : Array = c.source.filter( findFunction );
 return matches;
}

private function findFunction(propertyName:String,propertyValue:*):Function
{
   return function( element : *, index : int, array : Array ) : Boolean
   {
    return element[propertyName] == propertyValue;
   }
}

with the following usage

var ac:ArrayCollection=new ArrayCollection(
    [{name:'Ben', id:1, age:12},
     {name:'Jack', id:2, age:22},
     {name:'Joe', id:3, age:17}
    ]
);
var searchedElements:Array=findInCollection(ac,findFunction('id',2));

it will return an Array with the following object

{name:'Jack', id:2, age:22}

The drawback of this method is that we hard-code the property name with a String. This may be harmful for code maintenance.

---

'private var cmenu:ArrayCollection = new ArrayCollection([
    {id:"1", stuff:"whatever"},
    {id:"2", stuff:"whatever"},
    {id:"3", stuff:"whatever"}
]);

for(var i:int=0;i<cmenu.length;i++){
var num:Number=cmenu.getItemAt(i).id;
if(num==2){
var stuf:String=cmenu.getItemAt(i).stuff;
}
}'