Swift: Array contains(AnyObject) error Cannot convert type of ... throw -> Bool 错误

Question

为什么我使用 Array.contains(AnyObject) 来检查此数组中是否存在结构对象。它会出错:“无法转换类型 ... throw -> Bool”

struct DecorationPatternsData {
    let patternImageName: String
    init(patternImageName: String) {
        self.patternImageName = patternImageName
    }
}
var decorationPatterns : [DecorationPatternsData] = [DecorationPatternsData(patternImageName: "decoration1.gif"), DecorationPatternsData(patternImageName: "decoration1.gif"), DecorationPatternsData(patternImageName: "decoration1.gif")]

var pickedDecorationPattern : DecorationPatternsData? = nil

...

if (pickedDecorationPattern != nil) {
     if (decorationPatterns.contains(pickedDecorationPattern)) {  
         // Error: Cannot convert type of ... throw -> Bool
     }
}

Answer 1

那是因为您的 DecorationPatternsData 不符合 Equatable，这是 contains(_:) 工作的要求。

---

解决方案一:

extension DecorationPatternsData: Equatable { }

func ==(lhs: DecorationPatternsData, rhs: DecorationPatternsData) -> Bool {
    return lhs.patternImageName == rhs.patternImageName
}

现在 DecorationPatternsData 符合 Equatable 所以你可以使用:

if let pickedDecorationPattern = pickedDecorationPattern {
    if decorationPatterns.contains(pickedDecorationPattern) {
    // Your code
    }
}

解决方案 2:

if decorationPatterns.contains({ $0 == pickedDecorationPattern }) {
    // Your code
}

这里您使用闭包来比较元素，为 contains(_:) 返回一个 bool 值