CODEWITHSUNDEEP
swiftstructcollectionsvalue-typecopy-on-write
SwiftyFinch
SwiftyFinch

Reputation: 475

Which value types in Swift supports copy-on-write?

I read about copy-on-write implementation for Array in Swift here.

Arrays, like all variable-size collections in the standard library, use copy-on-write optimization. Multiple copies of an array share the same storage until you modify one of the copies. When that happens, the array being modified replaces its storage with a uniquely owned copy of itself, which is then modified in place. Optimizations are sometimes applied that can reduce the amount of copying.

I was wondering if you have any information about which structure supports copy-on-write.

Upvotes: 8

Views: 2380

Answers (1)

Dalija Prasnikar
Dalija Prasnikar

Reputation: 28517

Copy-on write is supported for String and all collection types - Array, Dictionary and Set.

Besides that, compiler is free to optimize any struct access and effectively give you copy-on-write semantics, but it is not guaranteed.

Upvotes: 10

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