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
    }
}

What's the code before that statement? It works fine for me by itself — Connor Pearson, Jun 28 '14 at 14:50
"declaration Operators are only allowed at global scope" Pretty darned clear. This is one of Swift's better compiler error messages! — matt, Jun 28 '14 at 15:01
You need to move `func ==(lhs: Cookie, rhs: Cookie) -> Bool {...}` OUT of the Cookie class!! — Hlung, Apr 12 '15 at 07:22

score 145 · Accepted Answer · answered Jun 28 '14 at 14:58

145

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.

answered Jun 28 '14 at 14:58

Connor Pearson

63,902
28
145
142

3

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. – fangmobile May 22 '15 at 23:33
2

I would've never thought to put it _outside_ the class! What's that even called? How do I find it on google? – rr1g0 Dec 24 '15 at 05:57
1

There's [an explanation about why the operator overload is in the global scope](http://stackoverflow.com/q/35246003/4151918), although a possible change is being discussed to let the operator implementation be inside the type. – Feb 10 '16 at 21:31

score 32 · Answer 2 · edited Jun 29 '17 at 16:33

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
    }

Felipe Ignacio Noriega Alcaraz · Answer 3 · 2015-09-06T13:05:41.463

6

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

class Cookie: NSObject {
...
}

(got the tip from the iOS apprentice tutorials)

edited Sep 06 '15 at 13:05

answered Sep 06 '15 at 12:58

Felipe Ignacio Noriega Alcaraz

235
3
8

1

That would be because NSObject implements the following on line 70 of the NSObject swiftDoc `extension NSObject : Equatable, Hashable`. – Adrian Sluyters Sep 20 '15 at 03:47

Swift Equatable Protocol

EDIT:

3 Answers3

Linked

Related