我在xcode7上遇到了一个错误迅速。

I got an error swift on xcode7.

该错误告诉我"'？'：'表达式中的结果值具有不匹配的类型'NSJONWritingOptions'和'_'"。有谁知道如何解决这一问题？我在xcode6.3.1上编写了这些代码，并立即将其转换为xcode7。虽然在xcode6上工作....

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public func toString(pretty:Bool=false)->String {
switch _value {
case is NSError: return"\\(_value)"
case is NSNull: return"null"
case let o as NSNumber:
switch String.fromCString(o.objCType)! {
case"c","C":
return o.boolValue.description
case"q","l","i","s":
return o.longLongValue.description
case"Q","L","I","S":
return o.unsignedLongLongValue.description
default:
switch o.doubleValue {
case 0.0/0.0: return"0.0/0.0" // NaN
case -1.0/0.0: return"-1.0/0.0" // -infinity
case +1.0/0.0: return"+1.0/0.0" // infinity
default:
return o.doubleValue.description
}
}
case let o as NSString:
return o.debugDescription
default:
let opts = pretty
//below is the code I got an error for
? NSJSONWritingOptions.PrettyPrinted : nil
if let data = (try? NSJSONSerialization.dataWithJSONObject(
_value, options:opts)) as NSData? {
if let result = NSString(
data:data, encoding:NSUTF8StringEncoding
) as? String {
return result
}
}
return"YOU ARE NOT SUPPOSED TO SEE THIS!"
}
}