Question

我有一个Int，我在Parse中保存为AnyObject。当我检索AnyObject？并尝试将其转换为String，NSString，NSNumber或其他任何东西，我继续得到一个EXC_Breakpoint，因为演员正在返回Nil并且那里有一个＆＃34; Swift动态演员失败＆＃34;错误＆＃34 ;.

我试图创建这个简单的测试以确定哪个部分失败了，但是疯狂的是这个测试将通过看似所有步骤都相同的地方：

func testAnyObjectCasting(){
    var myInt32: Int32 = 265
    var myInt: Int = Int(myInt32)
    var myAnyObject: AnyObject? = myInt as AnyObject
    var myAnyArray: [[AnyObject]] = [[AnyObject]]()
    myAnyArray.append(["something", myAnyObject!])
    println(myAnyObject)
    var myOtherAnyObject: AnyObject? = myAnyArray[0][1]
    println(myOtherAnyObject)
    var myString:NSNumber? = myOtherAnyObject as? NSNumber
    println(myString)
    var myInt2: Int = myString! as Int
}

这里是我的逻辑中的相关代码片段，并注意到println（）正常工作，直到向下转换为NSNumber，此时返回Nil：

   //ABRecordGetRecordId returns an ABRecordID, which is of type Int32
   //This value that's stored in the 2nd column of the multiDim [[AnyObject]] 
   var personId: Int = Int(ABRecordGetRecordID(person))

   //This is a call to a Parse object, which returns an AnyObject.  I then cast that to
   //a multidimensional array AnyObject as that's the true structure of the data in swift speak
   var deviceContacts: [[AnyObject]] = device?[deviceContactsFieldName] as [[AnyObject]]

   //This returns the expected value, which in my broader test case is 99999, which is supported by Int
   var i:Int = 1
   println("the value in device contacts \(i) column 1 is: \(deviceContacts[i][1])")

   //This takes a single cell value from the multidim array and puts it in an optional AnyObject
   var valueInParse: AnyObject? = deviceContacts[i][1]

   //This still returns 99999
   println(valueInParse)

   //This is where 99999 is replaced with nil.  Any ideas?
   var valueNSNumberInParse: NSNumber? = valueInParse as? NSNumber

   //Nil :(
   println(valueNSNumberInParse)

   //Exception as I'm trying to unwrap nil :( 
   var unwrappedNSNumber:NSNumber = valueNSNumberInParse!

我感到沮丧的部分原因是我不明白为什么println（）适用于AnyObject但是所有的转换都失败了。显然，那里的代码可以将值解释为为println显示的字符串，但是这种语法使我无法正确投射。

Answer 1

因为您已将Int保存到Parse并且Int不是对象，所以它必须转换为对象。似乎Parse框架已将其转换为NSValue，NSValue实际上是表示内部类型的字节缓冲区。

您可以尝试将这些字节转换回Int，但是在将值存储到Parse对象之前将值编码为NSNumber更容易也更好 - 然后在检索对象时您将能够轻松地处理它。

Swift AnyObject as String动态转换失败

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