Are standard array collections value types or reference types?

Arrays (Array) in Swift are structures (struct), and structures are value types (Value Types). When assigning or passing an array, it is copied.

However, for performance optimization, the array copying system employs Copy-on-Write behavior. This means that the actual data copy of the array occurs only upon the first modification of one of the copies. Until then, both copies share the same data storage.

Value types: Struct, Enum, Int, String, Double, Bool. Reference types: Class, Function, Closure.

Example illustrating Copy-on-Write:

var initialArray = [1, 2, 3]
var copiedArray = initialArray // No actual data copying yet

print(initialArray[0]) // 1
print(copiedArray[0])  // 1

copiedArray[0] = 10     // Actual data copying occurs here

print(initialArray[0]) // 1 (original array remains unchanged)
print(copiedArray[0])  // 10 (only the copied version changed)