How to determine if an associative array has a key?

Question

In ActionScript 3, is there any convenient way of determining if an associative array (dictionary) has a particular key?

I need to perform additional logic if the key is missing. I could catch the undefined property exception, but I'm hoping that can be my last resort.

Answer 1

Try this:

for (var key in myArray) {
    if (key == myKey) trace(myKey+' found. has value: '+myArray['key']);
}

Answer 2

The quickest way may be the simplest:

// creates 2 instances
var obj1:Object = new Object();
var obj2:Object = new Object();

// creates the dictionary
var dict:Dictionary = new Dictionary();

// adding the first object to the dictionary (but not the second one)
dict[obj1] = "added";

// checks whether the keys exist
var test1:Boolean = (dict[obj1] != undefined); 
var test2:Boolean = (dict[obj2] != undefined); 

// outputs the result
trace(test1,test2);

Answer 3

var card:Object = {name:"Tom"};

trace("age" in card);  //  return false 
trace("name" in card);  //  return true

Try this operator : "in"

Answer 4

hasOwnPropery is one way you test for it. Take this for example:

var dict: Dictionary = new Dictionary();

// this will be false because "foo" doesn't exist
trace(dict.hasOwnProperty("foo"));

// add foo
dict["foo"] = "bar";

// now this will be true because "foo" does exist
trace(dict.hasOwnProperty("foo"));