Ios pathExtension不可用：请改为在NSURL上使用pathExtension。Swift 2.0

我从文档目录中获取mp3文件，我写道pathExtension等于“mp3”，在Swift 1.2中它可以工作，但在Swift 2.0中我得到错误“'pathExtension'不可用：在NSURL上使用pathExtension。”

---

只需更改顺序：首先是

过滤器

，然后是

映射

。现在，将方法

pathExtension

应用于NSURL对象

listOfMP3Files = directoryURLs.filter { $0.pathExtension == "mp3" }.map { $0.lastPathComponent! }

您可以使用

尾随闭包

规则省略

过滤器

和

映射

之后的一对括号

---

Apple已从

String

中删除与路径相关的API，以选择更合适的

URL

，或者您可以使用此扩展：

extension String {
    var ns: NSString {
        return self as NSString
    }
    var pathExtension: String {
        return ns.pathExtension
    }
    var lastPathComponent: String {
        return ns.lastPathComponent
    }
}

---

Xcode 8.3.2•Swift 3.1

extension String {
    var fileURL: URL {
        return URL(fileURLWithPath: self)
    }
    var pathExtension: String {
        return fileURL.pathExtension
    }
    var lastPathComponent: String {
        return fileURL.lastPathComponent
    }
}

要使其向后兼容Swift 2.0中的1.2，请执行以下操作：

改进@Dharmesh Kheni的版本

extension String {
  var ns: NSString {
    return self as NSString
  }
  var pathExtension: String {
    return ns.pathExtension ?? ""
 }
  var lastPathComponent: String {
    return ns.lastPathComponent ?? ""
   }
}

---

我结合了达尔梅什和利奥的方法，让我的扩展工作：

  extension String { 
      public var url: NSURL {
         return NSURL(fileURLWithPath:self)
      }
      public var stringByDeletingLastPathComponent: String {
         return String(url.URLByDeletingLastPathComponent)
      }
 }

基于此，此扩展将在许多情况下帮助您

extension String {

    var lastPathComponent: String {
        get {
            return (self as NSString).lastPathComponent
        }
    }

    var pathExtension: String {
        get {

            return (self as NSString).pathExtension
        }
    }

    var stringByDeletingLastPathComponent: String {
        get {

            return (self as NSString).stringByDeletingLastPathComponent
        }
    }

    var stringByDeletingPathExtension: String {
        get {

            return (self as NSString).stringByDeletingPathExtension
        }
    }

    var pathComponents: [String] {
        get {

            return (self as NSString).pathComponents
        }
    }

    func stringByAppendingPathComponent(path: String) -> String {

        let nsSt = self as NSString

        return nsSt.stringByAppendingPathComponent(path)
    }

    func stringByAppendingPathExtension(ext: String) -> String? {

        let nsSt = self as NSString

        return nsSt.stringByAppendingPathExtension(ext)
    }
}

---

看起来确实很不错，但NSString铸造可能更便宜；-）我需要结合Dharmesh和Leo的方法来让我的扩展工作：

扩展字符串{public var url:NSURL{return NSURL（fileURLWithPath:self）}public var stringByDeletingLastPathComponent:String{return String（url.URLByDeletingLastPathComponent）}

extension String {

    var lastPathComponent: String {
        get {
            return (self as NSString).lastPathComponent
        }
    }

    var pathExtension: String {
        get {

            return (self as NSString).pathExtension
        }
    }

    var stringByDeletingLastPathComponent: String {
        get {

            return (self as NSString).stringByDeletingLastPathComponent
        }
    }

    var stringByDeletingPathExtension: String {
        get {

            return (self as NSString).stringByDeletingPathExtension
        }
    }

    var pathComponents: [String] {
        get {

            return (self as NSString).pathComponents
        }
    }

    func stringByAppendingPathComponent(path: String) -> String {

        let nsSt = self as NSString

        return nsSt.stringByAppendingPathComponent(path)
    }

    func stringByAppendingPathExtension(ext: String) -> String? {

        let nsSt = self as NSString

        return nsSt.stringByAppendingPathExtension(ext)
    }
}