[英]How to compare Enum in swift?
在Objective-C中這很好用
無法在Swift中編譯它
要么
IOS SDK中的ALAuthorizationStatus定義
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.
}
比較運算符==
返回Bool
,而不是Boolean
。 以下編譯:
func isAuthorized() -> Bool {
let status = ALAssetsLibrary.authorizationStatus()
return status == ALAuthorizationStatus.Authorized
}
(就個人而言,我發現來自Swift編譯器的錯誤消息有時令人困惑。在這種情況下,問題不是==
的參數,而是錯誤的返回類型。)
實際上,由於自動類型推斷 ,還應編譯以下內容:
func isAuthorized() -> Bool {
let status = ALAssetsLibrary.authorizationStatus()
return status == .Authorized
}
但它失敗了編譯器錯誤“找不到成員'授權'” ,除非您明確指定status
變量的類型:
func isAuthorized() -> Bool {
let status:ALAuthorizationStatus = ALAssetsLibrary.authorizationStatus()
return status == .Authorized
}
這可能是當前Swift編譯器中的一個錯誤(使用Xcode 6 beta 1測試)。
更新:第一個版本現在在Xcode 6.1中編譯。
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