Why Closures causing retain cycles in Swift? - Purpose & Use Cases

The Big Idea

Discover why your app might be stuck holding on too tightly and how to gently let go!

The Scenario

Imagine you have two friends who keep calling each other endlessly without stopping. In programming, this happens when two parts of your code keep holding on to each other, never letting go.

The Problem

When closures and objects hold strong references to each other, they create a loop. This means the memory they use never gets freed, causing your app to slow down or crash. Manually tracking and fixing these loops is tricky and error-prone.

The Solution

Understanding how closures capture variables and using tools like weak or unowned references helps break these loops. This way, your app uses memory efficiently and runs smoothly without unexpected crashes.

Before vs After

✗ Before

class Person {
  var closure: (() -> Void)?
  func setup() {
    closure = { print(self) }
  }
}

✓ After

class Person {
  var closure: (() -> Void)?
  func setup() {
    closure = { [weak self] in print(self) }
  }
}

What It Enables

It enables your app to manage memory smartly, preventing leaks and keeping performance high.

Real Life Example

Think of a photo app where a photo object holds a closure to update UI, and the closure holds the photo object back. Without fixing this, the app never frees memory, causing slowdowns.

Key Takeaways

Closures can hold strong references causing memory loops.

These loops prevent memory from being freed, hurting app performance.

Using weak or unowned references in closures breaks these loops.