What does this this ActionScript syntax mean? ( Syntax for returning Objects Inline )

Question

Hi,

I am a Java programmer and need to work on a Flex/ActionScript project right now. I got an example of using ITreeDataDesriptor from Flex 3 Cookbook, but there is one line of actionscript code that's hard for me to understand. I appreciate if someone could explain this a little further.

public function getData(node:Object, model:Object=null):Object
 {
  if (node is Office) {
   return {children:{label:node.name, label:node.address}};
  }
 }

The part that I didn't understand was "{children:{label:node.name, label:node.address}}". Office is simply a value object that contains two String properties: name and address.

Answer 1

I think in Java you would call that a map or an associative array. In Javascript and Actionscript you can say this to create an object with certain properties:

var myobject = {
   'prop1': 100,
   'prop2': {
      'a': 1
   }
}

trace( myobject.prop1 );   // 100
trace( myobject.prop2.a );   // 1

In your example it's just returned as a nameless object.

Answer 2

return {children:{label:node.name, label:node.address}};

Means you are returning a new Object. The {} are the Object's constructor, and in this case its an Anonymous object.

Answer 3

Thank you both for the quick response. So if I understand your explanations correctly, the return statement is returning an anonymous object, and this object has only one property named "children", which is again an associative array - ok, here is the part I don't quite understand still, it seems that both properties in this array are named "label", is this allowed?

Answer 4

The following return expression (modified from the question) ...

return {children:{label:node.name, body:node.address}}

... is functionally equivalent to this code ...

var obj:Object = new Object();
obj.children = new Object();
obj.children.label = node.name;
obj.children.body = node.address;
return obj;

The anonymous object returned in the question code complicates matters because it defines a property twice. In that case, the first declaration is used, and the subsequent one(s) are ignored. No compile-time or runtime error is thrown.