背景
我正在尝试使用NSCoding协议对String样式的枚举进行编码,但是我遇到了转换为String和从String返回的错误。
解码和编码时出现以下错误:
字符串不可转换为舞台
额外参数ForKey:通话中
码
enum Stage : String { case DisplayAll = "Display All" case HideQuarter = "Hide Quarter" case HideHalf = "Hide Half" case HideTwoThirds = "Hide Two Thirds" case HideAll = "Hide All" } class AppState : NSCoding, NSObject { var idx = 0 var stage = Stage.DisplayAll override init() {} required init(coder aDecoder: NSCoder) { self.idx = aDecoder.decodeIntegerForKey( "idx" ) self.stage = aDecoder.decodeObjectForKey( "stage" ) as String // ERROR } func encodeWithCoder(aCoder: NSCoder) { aCoder.encodeInteger( self.idx, forKey:"idx" ) aCoder.encodeObject( self.stage as String, forKey:"stage" ) // ERROR } // ... }
您需要将枚举值与原始值进行转换。在Swift 1.2(Xcode 6.3)中,如下所示:
class AppState : NSObject, NSCoding { var idx = 0 var stage = Stage.DisplayAll override init() {} required init(coder aDecoder: NSCoder) { self.idx = aDecoder.decodeIntegerForKey( "idx" ) self.stage = Stage(rawValue: (aDecoder.decodeObjectForKey( "stage" ) as! String)) ?? .DisplayAll } func encodeWithCoder(aCoder: NSCoder) { aCoder.encodeInteger( self.idx, forKey:"idx" ) aCoder.encodeObject( self.stage.rawValue, forKey:"stage" ) } // ... }
Swift 1.1(Xcode 6.1),as代替as!:
as
as!
self.stage = Stage(rawValue: (aDecoder.decodeObjectForKey( "stage" ) as String)) ?? .DisplayAll
迅速1.0(6.0的Xcode)使用toRaw()和fromRaw()这样的:
toRaw()
fromRaw()
self.stage = Stage.fromRaw(aDecoder.decodeObjectForKey( "stage" ) as String) ?? .DisplayAll aCoder.encodeObject( self.stage.toRaw(), forKey:"stage" )