Swift Equatable Protocol

问题

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
    }
}

回答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.

回答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
    }

回答3:

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

class Cookie: NSObject {
...
}

(got the tip from the iOS apprentice tutorials)

来源：https://stackoverflow.com/questions/24467960/swift-equatable-protocol

标签

ios

swift

xcode6