xcode - 错误 : value of tuple type '(NSString, NSString)' has no member '0'

Question

我正在尝试修改一些一年前运行良好的 Swift 源代码；但是自从 Apple 发布了 Swift 2.0 之后，Xcode 拒绝直接运行我现有的代码；坚持要我更新它以使用新的 Swift。谢谢苹果。

那么，任何人都可以解释这个完全愚蠢的错误吗？

value of tuple type '(NSString, NSString)' has no member '0'

失败的代码行:

if let match = (try Filesystem.GetMounts()?.filter { 
        mapping["pattern"] != nil ? try $0.0 =~ mapping["pattern"]! : $0.0 as String == uncpath! 
    }.values.array.first) {
    ...
}

GetMounts 函数签名:

class func GetMounts() throws -> [NSString:NSString]?

正则表达式运算符:

func =~(string:NSString, regex:NSRegularExpression) -> Bool {
    let matches = regex.numberOfMatchesInString(string as String, options: [], range: NSMakeRange(0, string.length))
    return matches > 0
}
func =~(string:NSString, pattern:NSString) throws -> Bool {
    let matches = try NSRegularExpression(pattern: pattern as String, options: NSRegularExpressionOptions.DotMatchesLineSeparators).numberOfMatchesInString(string as String, options: [], range: NSMakeRange(0, string.length))
    return matches > 0
}
func =~(string:NSString, pattern:String) throws -> Bool {
    let matches = try NSRegularExpression(pattern: pattern as String, options: NSRegularExpressionOptions.DotMatchesLineSeparators).numberOfMatchesInString(string as String, options: [], range: NSMakeRange(0, string.length))
    return matches > 0
}

Answer 1

问题是您试图提取不存在的属性 .values来自元组数组(NSString:NSString) .然而，这个真正的错误被提示 .0 所掩盖。元组的成员。

例如。以下产生与您得到的相同的错误:

let a: [NSString:NSString] = ["Hello":"World", "foo":"bar"]

let opt : Int? = 1
if let b = (a.filter() {
    opt != nil ? $0.0 == "Hello" : $0.0 as String == "foo"
    }.values.array.first) { // <-- actual error
        // ...
}

而以下不是:

let a: [NSString:NSString] = ["Hello":"World", "foo":"bar"]

let opt : Int? = 1
if let b = (a.filter() {
    opt != nil ? $0.0 == "Hello" : $0.0 as String == "foo"
    }.first) {
        print(b) // (Hello, World)
}