如何在 swift 中使用 NSCoder 对枚举进行编码? [英] How do I encode enum using NSCoder in swift?
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问题描述
背景
我正在尝试使用 NSCoding 协议对 String 样式的枚举进行编码,但在从 String 转换和返回时遇到错误.
I am trying to encode a String-style enum using the NSCoding protocol, but I am running into errors converting to and back from String.
我在解码和编码时遇到以下错误:
I get the following errors while decoding and encoding:
String 不能转换为 Stage
额外参数 ForKey: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
}
// ...
}
推荐答案
您需要将枚举与原始值相互转换.在 Swift 1.2 (Xcode 6.3) 中,这看起来像这样:
You need to convert the enum to and from the raw value. In Swift 1.2 (Xcode 6.3), this would look like this:
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),使用 as
而不是 as!
:
Swift 1.1 (Xcode 6.1), uses as
instead of as!
:
self.stage = Stage(rawValue: (aDecoder.decodeObjectForKey( "stage" ) as String)) ?? .DisplayAll
Swift 1.0 (Xcode 6.0) 像这样使用 toRaw()
和 fromRaw()
:
Swift 1.0 (Xcode 6.0) uses toRaw()
and fromRaw()
like this:
self.stage = Stage.fromRaw(aDecoder.decodeObjectForKey( "stage" ) as String) ?? .DisplayAll
aCoder.encodeObject( self.stage.toRaw(), forKey:"stage" )
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