iOS Swift 3: Comparing One all elements of Array in another array

Question

I have struct model like

struct ModelA {
    let text: String
    let id: Int
}

extension ModelA: Equatable {}

func ==(lhs: ModelA, rhs: ModelA) -> Bool {
    let areEqual = lhs.id == rhs.id
    return areEqual
}

i have created arrays of this model

let a1:[ModelA] = [ModelA(text: "10", id: 11), ModelA(text: "11", id: 12)]
let a2:[ModelA] = [ModelA(text: "11", id: 12)]

and having a comparing function

func isEqualArray(first array1: [Any], second array2: [Any]) -> Bool {
     let set1 = NSSet(array: array1)
     let set2 = NSSet(array: array2)
     return set1.isSubset(of: set2 as! Set<AnyHashable>)
}

so when i'm trying to cross check

 let flag = isEqualArray(first: a1, second: a2)
 print("### \(flag)")

It crashes on function return

What am I doing wrong?

Your struct needs to conform to hashable as well as equatable — Paulw11
– Paulw11, Commented Aug 3, 2017 at 3:54
why are you using NSSet instead of Swift sets? And any time you use ! you are asking for your code to crash if the downcast fails. — Paulw11
– Paulw11, Commented Aug 3, 2017 at 3:55

Paulw11 · Accepted Answer · 2017-08-03 04:10:14Z

1

Your struct needs to conform to both equatable and hashable in order to be used in a Set. It seems that you only care about the id, so a simple implementation would be:

struct ModelA {
    let text: String
    let id: Int
}

extension ModelA: Equatable {
    static func ==(lhs: ModelA, rhs: ModelA) -> Bool {
        return lhs.id == rhs.id
    }
}

extension ModelA: Hashable {
    var hashValue: Int {
        return id
    }
}

Now, you can use Swift sets in your isEqualArray function; you also need to consider which set is smaller since you are using isSubSet(of:):

func isEqualArray(first array1: [AnyHashable], second array2: [AnyHashable]) -> Bool {

    let set1: Set<AnyHashable>
    let set2: Set<AnyHashable>

    if array1.count > array2.count {
        set1 = Set(array1)
        set2 = Set(array2)
    } else {
        set1 = Set(array2)
        set2 = Set(array1)
    }
    return set2.isSubset(of: set1)
}

Your code actually determines if one array is a subset of another, not if the arrays are equal, so I am not sure if that is what you want.

answered Aug 3, 2017 at 4:10

Paulw11

116k15 gold badges175 silver badges213 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Paulw11 Over a year ago

As I said, your code is using isSubSet(Of:), so you need to know which array is larger, a larger set cannot be a subset of a smaller set

Collectives™ on Stack Overflow

iOS Swift 3: Comparing One all elements of Array in another array

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related