Memory & ARC in Kotlin/Native

On iOS your Kotlin objects and Apple objects coexist. Kotlin/Native uses its own collector, while Apple uses ARC reference counting under the hood.

ARC, Automatic Reference Counting, frees an Objective-C object once nothing references it. It is automatic, but it still tracks ownership precisely. 🧮

Kotlin objects are managed by a garbage collector, not by counting. You rarely free anything by hand, but you do help by dropping stale references.

When a Kotlin object holds an Apple object, the runtime keeps the right counts so neither side frees memory too early. The boundary stays consistent.

Modern Kotlin/Native uses a concurrent collector. It removed the old freezing rules, so sharing state across threads is far simpler than it once was. ✨

A retain cycle happens when two objects strongly hold each other, so neither is ever freed. This leaks memory on the Apple side.

Avoid cycles by not letting a child strongly hold its parent. Drop references when work finishes so the collector can reclaim the memory.

A Kotlin lambda passed to Apple code captures what it touches. If it captures self, you can form a cycle, so capture only what the closure truly needs.

Objects that live for the whole app, like a shared client, are fine if intentional. Just be sure a singleton is not pinning data it should release.

Xcode Instruments and the Leaks tool can spot growth from the Kotlin side too. Profiling shows whether your references are really being freed.

Let the collectors do their job, avoid strong cycles, and release big objects when done. That covers almost every memory concern in real KMP apps.

A quick check on cross-platform memory.

You learned that Kotlin uses a collector while Apple uses ARC, the runtime bridges them, and your job is mainly to avoid retain cycles. 🎉