如何在swift中比较Enum？
在Objective-C中，这工作正常
无法在Swift中进行编译
要么
IOS SDK中的ALAuthorizationStatus定义
enum ALAuthorizationStatus : Int {
case NotDetermined // User has not yet made a choice with regards to this application
case Restricted // This application is not authorized to access photo data.
// The user cannot change this application’s status, possibly due to active restrictions
// such as parental controls being in place.
case Denied // User has explicitly denied this application access to photos data.
case Authorized // User has authorized this application to access photos data.
}
比较运算符==返回一个Bool ，而不是Boolean 。 以下编译：
func isAuthorized() -> Bool {
let status = ALAssetsLibrary.authorizationStatus()
return status == ALAuthorizationStatus.Authorized
}
（就我个人而言，我发现Swift编译器的错误消息有时会令人困惑，在这种情况下，问题不是==的参数，而是不正确的返回类型。）
实际上，由于自动类型推断，下面也应该编译：
func isAuthorized() -> Bool {
let status = ALAssetsLibrary.authorizationStatus()
return status == .Authorized
}
但它会因编译器错误“Could not find member'Authorized'”而失败，除非您明确指定了status变量的类型：
func isAuthorized() -> Bool {
let status:ALAuthorizationStatus = ALAssetsLibrary.authorizationStatus()
return status == .Authorized
}
这可能是当前Swift编译器（用Xcode 6 beta 1测试）中的一个错误。
更新：第一个版本现在在Xcode 6.1中编译。
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