错误：元组类型“（NSString，NSString）”的值没有成员“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。感谢苹果。

那么，谁能解释一下这个完全愚蠢的错误？

元组类型'(NSString, NSString)'的值没有成员'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

问题是您试图从元组数组(NSString:NSString) 中提取不存在的属性.values。然而，这个真正的错误被抱怨 .0 元组的成员所掩盖。

例如以下会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)
}