The latest beta of Xcode 6 brings a much-needed revision to Swift’s arrays. Instead of the sometimes-value, sometimes-by-reference behavior, where “immutable” arrays could be modified and “copied” arrays maintained links to the original, arrays now act much more as one would expect. Constant arrays are truly constant and immutable, and copied arrays can’t have values changed with modifications to the source (or vice versa).
let names = ["Thomas", "Percy", "Rosie", "Daisy"] // actually immutable! > [Thomas, Percy, Rosie, Daisy] names = "Edward" // error