Understanding Copy-on-Write (CoW) in Swift

One of Swift's smartest optimizations is also one of its most misunderstood.

When you write:

var array2 = array1

Swift usually doesn't copy the data immediately.

Instead, it uses Copy-on-Write (CoW) and delays the copy until a mutation occurs.

This gives us:

1. Value semantics
2. Memory efficiency
3. Better performance
4. Safer code

Understanding CoW explains why Swift collections like Array, Dictionary, and Set are both fast and safe.

I recently explored how CoW works under the hood and why it matters for real-world Swift development.

Understanding Copy on Write (CoW) in Swift

#swift #ios #performance #programming