how to compare two optional NSArrays in Swift

Question

Let\'s have two optional NSArrays. The goal is to check, if they are equal. My solution is

func isArrayEqualToArray(array1:NSArray?, array2:NSArray?) -> B         


        

Answer 1

It is quite simple:

func isArrayEqualToArray(array1: NSArray?, array2: NSArray?) -> Bool {
    return array1 == array2
}

does exactly what you want.

Why does it work? Here == is the operator that compares optionals

func ==(lhs: T?, rhs: T?) -> Bool

and that gives true if both operands are nil, or of both operands are non-nil and the unwrapped operands are equal.

Also NSArray inherits from NSObject which conforms to Equatable, and comparing NSObjects with == uses the isEqual: method, which is implemented as isEqualToArray: on NSArray. Therefore

array1 == array2

gives the same result as

array1.isEqualToArray(array2)