Best Ever Implementation of "indexOf"!

December 07, 2009 at 10:31 PM | ActionScript | View Comments

(alternate title: The "Fail Early, Fail Often" Principle in Action)

I would like to award Adobe the "best ever implementation of indexOf". Ready for it? Here it is:

override flash_proxy function callProperty(name:*, ... rest):* {
    return null;

This beauty can be found in mx.collections.ListCollectionView.

And the kicker? The function's documentation:

 *  @private
 *  Any methods that can't be found on this class shouldn't be called,
 *  so return null

The author clearly knew that unknown methods* shouldn't be called… But instead of doing something sensible – like throwing an exception – they do something wholly nonsensical and return null. Or, of course, they could also have left the function unimplemented, which would result in a strange and unhelpful exception… But, of course, I would expect nothing but the best from the Flex standard library.

Next up: why implicit conversions from null to int are always wrong.


*: the magic callProperty method is called on subclasses of Proxy when a method can't be found. For example if bar is not a method of foo, executing call foo.callProperty("bar").

PS: Instead of calling indexOf, I should have been calling getItemIndex.