Question

Adobe specifically states about Dictionaries:

the object’s identity is used to look up the object, and not the value returned from calling toString()

However when I run

if(myInstance in myDictionary)  { ... }

To see if myInstance already exists as a ‘key’ in myDictionary, myInstance.tostring get’s called!

Anyone know why or a way around it?

Answer 1

The in keyword is generally used with object properties, which are strings. Consider the difference between a for each loop versus a for in loop.

We typically use the for in loop to iterate over an object’s dynamic properties:

private var o:Object = { property1: "value1", property2: "value2" };
for (var propertyName:String in o)
{
    trace(propertyName);
    trace(o[propertyName]);
}

Outputs:
property1
value1
property2
value2

So in your code snippet the in keyword is causing the call to toString().

The correct way to test if a key exists is to test for null:

if (myDictionary[myInstance])
    trace("key exists and it has a value");