In Xcode 4.x press
select the "Diagnostics" tab and click "Enable Zombie Objects":
This turns released objects into NSZombie instances that print console warnings when used again. This is a debugging aid that increases memory use (no object is really released) but improves error reporting.
A typical case is when you over-release an object and you don't know which one:
- With zombies:
-[UITableView release]: message sent to deallocated instance
- Without zombies:
This Xcode setting is ignored when you archive the application for App Store submission. You don't need to touch anything before releasing your application.
Pressing ⌥⌘R is the same as selecting Product > Run while keeping the Alt key pressed.
Clicking the "Enable Zombie Objects" checkbox is the same as manually adding "NSZombieEnabled = YES" in the section "Environment Variables" of the tab Arguments.