[eluser]bretticus[/eluser]
[quote author="jhabbley" date="1253095777"]
However, when the intended functionality of a core class causes problems, I think it's more efficient to correct the behavior at the source, rather than to add the overhead of extending a class. (detecting the extended class, loading the extended class, etc) This is especially true of a core class that is used on nearly every page.
Of course, this is my interpretation, and I'm certainly open to discussion.[/quote]
Funny you should mention that. Just tonight I have been stepping through the core files. I needed to extend the Config and Loader classes to use different views files for a mobile site if the host header matches the mobile site address. Anyways, I digress...
It appears to me that the MY_ extension libs in application are checked each time anyway and unless extends causes overhead, there's really no overhead using that method (unless you cause it within your extended class
)
I prefer not to update the core files in case they don't fix a bug in the next release. Which means if I upgrade the core files (next release), I've got to patch the core files again.