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

Yes, indeed, you don't need to overcomplicate things:

func isArrayEqualToArray(array1: NSArray?, array2: NSArray?) -> Bool {
    if array1 == nil && array2 == nil {
        return true;
    }

    if array1 != nil && array2 != nil {
        return array1!.isEqualToArray(array2!);
    }

    return false;
}

Answer 2

I liked @The Paramagnetic Croiss answer but I'm still going to shorten it a bit because I see that I can.

```

func isArrayEqualToArray(array1: NSArray?, array2: NSArray?) -> Bool {
    if array1 == array2 {
        return true;
    }
    if array1 != nil && array2 != nil {
        return array1!.isEqualToArray(array2!);
    }
    return false;
}

```

Answer 3

Using a switch statement may be clearer:

func isArrayEqualToArray(a1: NSArray?, a2: NSArray?) -> Bool {
    switch (a1,a2) {
        case (.Some(a1),.Some(a2)):
            return a1.isEqualToArray(a2)
        case (.None,.None):
            return true
        default:
            return false
    }
}

Answer 4

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 ==<T : Equatable>(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)