automatic reference counting

Automatic Reference Counting (ARC) is a memory management feature in Swift that automatically handles the memory of class instances. It works by keeping track of the number of references to each class instance. When there are no more references to an instance, ARC automatically deallocates it to free up memory.

In the context of the WWDC session titled "Analyze heap memory," several points about ARC and related memory management techniques are discussed:

1. Retain and Release Overhead: It's important not to circumvent ARC, as manual reference counting can lead to hard-to-debug memory leaks. Instead, techniques like marking methods as @objc direct for inlining or using the @objc externally retained attribute can help reduce retain and release traffic.

2. Weak and Unowned References: These are alternatives to strong references that can help manage memory more efficiently. Weak references are a good default, while unowned references save memory and time when you can guarantee a reference won't outlive its destination.

3. Autorelease Pools: Swift can produce autoreleased objects when interacting with Objective-C APIs. Managing autorelease pool growth is crucial to prevent temporary memory spikes, especially in loops.

4. Profiling and Optimization: Profiling can help identify hotspots related to automatic retain and release calls. Enabling whole module optimization and specializing generics can reduce overhead.

For more detailed insights, you can refer to the session Analyze heap memory (30:44) where reducing reference counting overhead is discussed.