Swift Equatable Protocol

Question

I was folling this tutorial for Swift: https://www.raywenderlich.com/125311/make-game-like-candy-crush-spritekit-swift-part-1 and came across this code:

func == (lhs: Cookie, rhs: Cookie) -> Bool {
    return lhs.column == rhs.column && lhs.row == rhs.row
}

I wrote exactly that, but Xcode is giving my these errors:

Consecutive declarations on a line must be separated by ';'
Expected declaration operators are only allowed at global scope

I found this code from apple's documentation: https://developer.apple.com/documentation/swift/equatable

Which is very similar to what I wrote. Whats wrong? This seems like a bug to me. I am using Xcode 6 Beta 2

EDIT:

This is my whole Cookie class:

class Cookie: Printable, Hashable {
    var column: Int
    var row: Int
    let cookieType: CookieType
    let sprite: SKSpriteNode?
    
    init(column: Int, row: Int, cookieType: CookieType) {
        self.column = column
        self.row = row
        self.cookieType = cookieType
    }
    
    var description: String {
        return "type:\(cookieType) square:(\(column),\(row))"
    }
    
    var hashValue: Int {
        return row * 10 + column
    }
    
    func ==(lhs: Cookie, rhs: Cookie) -> Bool {
        return lhs.column == rhs.column && lhs.row == rhs.row
    }
}

Unhandy

What's the code before that statement? It works fine for me by itself – Annmarie

I added the whole class to the description – Unhandy

"declaration Operators are only allowed at global scope" Pretty darned clear. This is one of Swift's better compiler error messages! – Hawkie

you can overload an operator in the file-scope only. – Jequirity

You need to move func ==(lhs: Cookie, rhs: Cookie) -> Bool {...} OUT of the Cookie class!! – Hiero

Answer 1

Move this function

func == (lhs: Cookie, rhs: Cookie) -> Bool {
    return lhs.column == rhs.column && lhs.row == rhs.row
}

Outside of the cookie class. It makes sense this way since it's overriding the == operator at the global scope when it is used on two Cookies.

Annmarie

I would like to add that on xCode 6.3.2 and swfit 1.2, func == must be immediately after the class or struct definition. Even adding a simple sentence like "var a = 1" will bring back the compiler error. – Shedd

I would've never thought to put it outside the class! What's that even called? How do I find it on google? – Hypoderma

There's an explanation about why the operator overload is in the global scope, although a possible change is being discussed to let the operator implementation be inside the type. – Mirandamire

Answer 2

SWIFT 2:

As in swift 2 NSObject already conforms to Equatable.You don't need conformance at the top so it's like

class Cookie: NSObject {
    ...

}

And you need to override isEqual method as

class Cookie:NSObject{
    var column: Int
    var row: Int

    //..........

    override func isEqual(object: AnyObject?) -> Bool {
        guard let rhs = object as? Cookie else {
            return false
        }
        let lhs = self

        return lhs.column == rhs.column
    }

}

This time isEqual method is inside the class. :)

EDIT for SWIFT 3: Change this method as

override func isEqual(_ object: AnyObject?) -> Bool {
        guard let rhs = object as? Cookie else {
            return false
        }
        let lhs = self

        return lhs.column == rhs.column
    }

Deloris

Answer 3

making the class an NSObject solved the equatable problems for me...

class Cookie: NSObject {
...
}

(got the tip from the iOS apprentice tutorials)

Delainedelainey

That would be because NSObject implements the following on line 70 of the NSObject swiftDoc extension NSObject : Equatable, Hashable. – Talie