arrays - 类型 'String?' 不符合协议(protocol) 'Equatable'

Question

在我下面的代码中，winRankArray 的内容都是字符串对象。我遇到的问题是在最后设置 didWinRank 变量会出现以下错误:

Type 'String?' does not conform to protocol 'Equatable'

我尝试删除？，以便设置卡牌等级看起来像var cardRank1 = DeckDictionary[cardKey1].first，但这给了我一个错误，指出

Value of optional type 'Array?' not unwrapped; did you mean to use '!' or '?'?

如何设置变量以使生成的 winRankArray 不会出现此问题？

        var cardKey1 = "card\(firstRandomNumber)"
        var cardRank1 = deckDictionary[cardKey1]?.first

        var cardKey2 = "card\(firstRandomNumber)"
        var cardRank2 = deckDictionary[cardKey2]?.first

        var cardKey3 = "card\(firstRandomNumber)"
        var cardRank3 = deckDictionary[cardKey3]?.first

        var cardKey4 = "card\(firstRandomNumber)"
        var cardRank4 = deckDictionary[cardKey4]?.first

        var cardKey5 = "card\(firstRandomNumber)"
        var cardRank5 = deckDictionary[cardKey5]?.first

        var cardKey6 = "card\(firstRandomNumber)"
        var cardRank6 = deckDictionary[cardKey6]?.first

        var cardKey7 = "card\(firstRandomNumber)"
        var cardRank7 = deckDictionary[cardKey7]?.first

        var winRankArray = [cardRank1, cardRank2, cardRank3, cardRank4, cardRank5, cardRank6, cardRank7]

        //func sameRank {loop through winRankArray, find 3 identical values, set winRankStatus to true}
        let didWinRank = winRankArray.slidingWindowWithLength(4).contains{ $0.allEqual() }

Answer 1

Type 'String?' does not conform to protocol 'Equatable'

我不这么认为...

var s1: String? = "alfa"
var s2: String? = nil
var s3: String? = "beta"
var arr: Array<String?> = [s1, s2, s3]
arr.contains { (str) -> Bool in  // true
    str == "alfa"
}
s1 == "alfa" // true
s1 == s3     // false
s2 == nil    // true

When adopting Equatable, only the == operator is required to be implemented. The standard library provides an implementation for !=.