从Google文档表单中订购电子表格中的列(Order columns in a spreadsheet from a google docs form)

 我不确定是否可以在不知道数组是如何构建的情况下回答问题。 一个问题是For-in循环变量是一个NSFastEnumerationIterator，因此它需要向下转换为你想要它的那种“东西”。 你可能已经这样做了，这只是为了将来的参考。 
 
 话虽如此，我制作了一些代码并将其分解了一下 - 也许它会指向正确的方向。 
 
 下面的代码通过.value读入所有节点，然后遍历快照并将每个子节点存储在数组中作为FDataSnapshot。 然后代码迭代该数组并从存储在数组中的每个快照打印“guardian”。 
 
 我还包括你的代码来打印guardianID，它也可以工作，所以我的猜测是问题在于如何最初填充数组或在此行中 
 
 
 
 用于self.guardians中的快照 
 
 
 因为快照是NSFastEnumerationIterator 
 
let ref = self.myRootRef.child(byAppendingPath: "guardian_node")!

ref.observe(.value, with: { snapshot in

     if ( snapshot!.value is NSNull ) {
          print("not found")
     } else {

          var guardianArray = [FDataSnapshot]()

          for child in snapshot!.children {
               let snap = child as! FDataSnapshot //downcast
               guardianArray.append(snap)
          }

          for child in guardianArray {
               let dict = child.value as! NSDictionary
               let thisGuardian = dict["guardian"]!
               print(thisGuardian)

               //your code
               let guardianID = (child.value as? NSDictionary)?["guardian"] as? NSString
               print(guardianID!)
          }
     }
})
 
 *这是Swift 3和Firebase 2.x，但概念是相同的。 

I am not sure if the question can be answered without knowing how the array is built. One gotcha is the For-in loops variable is a NSFastEnumerationIterator so it needs to be downcast to what kind of 'thing' you want it to be. You may have done that so this is just for future reference.
 
That being said, I crafted up some code and broke it down a bit - maybe it will point you in the right direction.
 
The code below reads in all nodes by .value and then iterates over the snapshot and stores each child in an array as a FDataSnapshot. Then the code iterates over that array and prints the 'guardian' from each snapshot stored in the array.
 
I also included your code to print the guardianID and it works as well so my guess is the problem lies with how the array is being initially populated or in this line
 
 
 
for snapshot in self.guardians
 
 
as the snapshot is a NSFastEnumerationIterator
 
let ref = self.myRootRef.child(byAppendingPath: "guardian_node")!

ref.observe(.value, with: { snapshot in

     if ( snapshot!.value is NSNull ) {
          print("not found")
     } else {

          var guardianArray = [FDataSnapshot]()

          for child in snapshot!.children {
               let snap = child as! FDataSnapshot //downcast
               guardianArray.append(snap)
          }

          for child in guardianArray {
               let dict = child.value as! NSDictionary
               let thisGuardian = dict["guardian"]!
               print(thisGuardian)

               //your code
               let guardianID = (child.value as? NSDictionary)?["guardian"] as? NSString
               print(guardianID!)
          }
     }
})
 
*This is Swift 3 and Firebase 2.x but the concept is the same.