[英]How do I convert a UserDefault value from AnyObject? to an Int so I can save it
I'm trying to learn how to work with UserDefaults and can't figure out how to store one of the values I need to store. 我正在尝试学习如何与UserDefaults一起使用,并且无法弄清楚如何存储需要存储的值之一。
I have this enum: 我有这个枚举:
enum CalculationFormula: Int {
case Epley
case Brzychi
case Lander
case Lombardi
case MayhewEtAl
case OConnerEtAl
}
and this class with a property called 'selectedFormula' that I want to be able to store as a NSUserDefaults value: 此类具有名为“ selectedFormula”的属性,我希望能够将其存储为NSUserDefaults值:
class CalculatorBrain: NSObject {
var weightLifted: Double
var repetitions: Double
var oneRepMax: Double?
var selectedFormula = CalculationFormula.Epley
init(weightLifted: Double, repetitions: Double) {
self.weightLifted = weightLifted
self.repetitions = repetitions
let userDefaults = NSUserDefaults.standardUserDefaults()
self.selectedFormula = userDefaults.objectForKey("selectedFormula") <-- error
}
The self.selectedFormula line gives me an error: self.selectedFormula行给我一个错误:
'Cannot assign value of type 'AnyObject?' to type 'CalculationFormula'
After much searching on SO and reading the Apple documentation I learned a lot about UserDefaults and AnyObject, but didn't find an answer. 在进行大量搜索并阅读了Apple文档之后,我学到了很多有关UserDefaults和AnyObject的知识,但是没有找到答案。
I thought I did when I tried to cast it as an Int: 当我尝试将其转换为Int时,我以为是这样做的:
self.selectedFormula = userDefaults.objectForKey("selectedFormula") as! Int
// 'Cannot assign value of type 'Int' to type 'CalculationFormula'
and 和
self.selectedFormula = userDefaults.objectForKey("selectedFormula") as Int
// 'Cannot convert value of type 'AnyObject?' to type 'Int' in coercion
I know the preference values need to be one of these types (NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary) but I'm storing an Int so I should be good there. 我知道首选项值必须是这些类型之一(NSData,NSString,NSNumber,NSDate,NSArray或NSDictionary),但是我要存储一个Int,所以我应该在那里。
I'm just stuck and would really appreciate some help. 我只是被困住了,非常感谢您的帮助。 Please and thank you.
谢谢,麻烦您了。
Since your enum 自从你的枚举
enum CalculationFormula: Int {
case Epley, Brzychi, Lander, Lombardi, MayhewEtAl, OConnerEtAl
}
extends Int
you can use its rawValue
. 扩展
Int
可以使用其rawValue
。 So you can read/save an Int
from/to NSUserDefaults
. 因此,您可以从
NSUserDefaults
读取/保存一个Int
。
func saveFormula(formula: CalculationFormula) {
NSUserDefaults.standardUserDefaults().setInteger(formula.rawValue, forKey: "selectedFormula")
}
func loadFormula() -> CalculationFormula? {
guard NSUserDefaults.standardUserDefaults().dictionaryRepresentation().keys.contains("selectedFormula") else {
print("No value found")
return nil
}
guard let retrievedFormula = CalculationFormula(rawValue: NSUserDefaults.standardUserDefaults().integerForKey("selectedFormula")) else {
print("Wrong value found")
return nil
}
return retrievedFormula
}
您必须使用rawValue
初始化枚举:
self.selectedFormula = CalculationFormula(rawValue: userDefaults.objectForKey("selectedFormula") as! Int)
You should save your value as: 您应该将值另存为:
userDefaults.setInteger(yourValue, forKey: "yourKey")
Load your value as: 将值加载为:
userDefaults.integerForKey("yourKey") // Returns 0 if the value is nil.
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