背景
我尝试使用NSCoding协议对字符串样式的枚举进行编码,但在字符串之间来回转换时遇到错误。
在解码和编码时,我得到了以下错误:
字符串不能转换为阶段
额外的参数ForKey:在调用中
代码
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
}
// ...
}
发布于 2014-10-12 23:26:54
您需要将枚举与原始值相互转换。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 (Xcode6.1)使用as
而不是as!
self.stage = Stage(rawValue: (aDecoder.decodeObjectForKey( "stage" ) as String)) ?? .DisplayAll
Swift 1.0 (Xcode6.0)使用toRaw()
和fromRaw()
,如下所示:
self.stage = Stage.fromRaw(aDecoder.decodeObjectForKey( "stage" ) as String) ?? .DisplayAll
aCoder.encodeObject( self.stage.toRaw(), forKey:"stage" )
发布于 2015-03-10 21:10:53
Xcode 6.3、Swift 1.2的更新:
self.stage = Stage(rawValue: aDecoder.decodeObjectForKey("stage") as! String) ?? .DisplayAll
请注意as!
发布于 2018-07-14 01:33:57
这是一个针对Swift 4.2的解决方案。正如在其他答案中所述,问题在于您尝试将stage
变量直接赋值给解码后的字符串,并尝试在encodeWithCoder
方法中将stage
变量转换为字符串。您需要改用原始值。
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.decodeInteger(forKey: "idx")
self.stage = Stage(rawValue: aDecoder.decodeObject(forKey: "stage") as String)
}
func encodeWithCoder(aCoder: NSCoder) {
aCoder.encode(self.idx, forKey:"idx")
aCoder.encode(self.stage.rawValue, forKey:"stage")
}
// ...
}
https://stackoverflow.com/questions/26326645
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