iOS Programming: The Big Nerd Ranch Guide

For the More Curious: Autorelease Pool and ARC History

Before automatic reference counting (ARC) was added to Objective-C, we had manual reference counting. With manual reference counting, ownership changes only happened when you sent an explicit message to an object.

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This was a bummer: Forgetting to send release to an object before setting a pointer to point at something else would create a memory leak. Sending release to an object if you had not previously sent retain to the object was a premature deallocation. A lot of time was spent debugging ...